GIFT  OF 
Pacific  Coast 
Journal  of* 


BIOLOGY 

LIBRARY 


i* 


APPLIED  CHEMISTRY 


APPLIED  CHEMISTRY 


AN  ELEMENTARY  TEXT  BOOK 
FOR   SECONDARY  SCHOOLS 


BY 


FREDUS  N.  PETERS,  PH.D. 

Instructor   in    Chemistry   in    Central    High    School,    Kansas   City,   Mo.,    for 

twenty-three  years;   More  Recently  Vice-Principal;   Author 

of    "Chemistry    for    Nurses,"    etc. 


ILLUSTRATED 


ST    LOUIS 

C.  V.  MOSBY  COMPANY 

1922 


ap3i 


B10LOGY 

R 
D 


GIFT  PACIFIC  00 AST  JOURNAL} 
OF  NUBS1NG  TO  H/QcJrtE  DEPT 


COPYRIGHT,  1922,  BY  THE  C.  V.  MOSBY  COMPANV. 
(All    rights    reserved) 


Printed  in  U.  S.  A. 


Press  of 

C.    V.  Mosby  Company 
St.   Louis 


o  the  hundreds  of  young  men 
and  women,  students  of  mine  in  the 
past,  whom  it  has  been  my  privilege 
to  know  and  to  love ;  especially  to 
my  own  son,  Fredus  Nelson,  Junior, 
who  in  his  early  childhood,  playing 
at  chemistry  among  the  bottles  and 
apparatus  of  my  laboratory,  found  his 
chief  delight  and  who  now  in  his 
early  manhood  gives  promise  of  at- 
taining to  heights  in  this  realm  of 
science  of  which  his  father  only 
dreamed,  this  little  book  is  affection- 
ately dedicated  by  the  author. 


743629 


PREFACE 

The  author  is  not  very  sure  but  that  the  preface  of  any 
book  is  a  useless  page.  It  is  doubtful  whether  a  sufficient 
number  ever  read  this  personal  letter  of  the  author  to 
pay  him  for  the  writing  or  the  publisher  for  printing  it. 
Yet  every  writer  by  force  of  custom  feels  compelled  to 
address  his  readers  by  a  foreword. 

Like  Livy,  in  his  preface  to  his  History  of  the  Roman 
People,  I  do  not  know  whether  I  am  doing  a  work  worth 
while  in  putting  another  text  of  elementary  chemistry  be- 
fore the  public ;  and  even  if  I  knew,  modesty  would  forbid 
that  I  speak  very  strongly. 

Permit  me  to  say  that  to  me  it  has  never  seemed  neces- 
sary for  a  high  school  chemistry  to  present  a  mere  skeleton 
of  the  most  interesting  of  sciences  when  that  skeleton  may 
just  as  easily  be  clothed  with  wonderful  symmetry  and 
charming  beauty.  On  the  contrary,  it  has  always  seemed 
that  a  text  for  secondary  schools  may  and  ought  to  be  a 
readable  book  just  as  well  as  one  merely  surfeited  with 
facts.  No  dinner  menu  is  complete  which  offers  nothing 
but  lean  meat  and  vegetables.  It  may  thus  contain  all  that 
is  essential,  but  far  from  all  that  is  desired.  Entrees  and 
desserts  round  out  the  repast  and  give  a  sense  of  satisfac- 
tion not  otherwise  possible. 

Such  is  the  attempt  of  this  text,  to  present  the  chemical 
facts  of  every-day  life  in  a  readable  form  and  by  so  doing 
make  them  interesting.  If  this  cannot  be  done,  for  most 
students  the  book  is  a  failure. 

To  the  teacher  let  me  say  that  my  long  experience  com- 
pels me  to  believe  that  very  few  classes,  in  a  school  year  of 
nine  or  ten  months,  are  able  to  complete  a  text  of  this  size. 

11 


12  PREFACE 

Some  portions  must  be  omitted.  No  one  in  a  table  d'hote 
dinner  is  expected  to  order  everything  on  the  bill  of  fare. 
Let  him  use  judgment  and  discretion,  the  teacher  likewise. 
Almost  a  quarter  of  a  century  has  elapsed  since  I  began 
my  work  in  Central  High  School  in  Kansas  City,  one  of 
the  great  high  schools  of  the  Middle  West.  I  should  not  be 
true  to  my  own  better  self  did  I  fail  to  acknowledge  my 
debt  of  gratitude  to  the  hundreds  of  students  whom  I  have 
had  in  that  time.  In  this  particular  work  I  wish  to  thank 
especially  Mr.  J.  U.  Young,  now  head  of  the  department 
of  Chemistry  of  Central  High  School,  Kansas  City,  for  his 
many  valuable  suggestions  and  also  Mr.  G.  W.  Davis,  of 
the  Northeast  High  School,  Kansas  City.  I  am  also  under 
obligations  to  Mr.  G.  H.  Wilkinson  of  the  Physics  Depart- 
ment of  Jefferson  High  School,  Los  Angeles,  Cal.,  who  has 
been  of  material  assistance  in  reading  the  manuscript ;  to 
Mr.  F.  N.  Peters,  Jr.,  of  the  Department  of  Chemistry  of 
the  University  of  Missouri,  for  suggestions  in  methods  of 
presentation  of  certain  gas  laws,  to  Mr.  V.  W.  Peters,  of 
Los  Angeles,  Cal.,  for  drawings  from  which  many  of  the 
illustrations  were  made ;  to  the  Goldschmidt  Thermit  Co., 
of  New  York  City,  for  illustrations  of  thermit  welding,  to 
the  Permutit  Water  Softener  Co.,  of  New  York,  as  well  as 
to  two  or  three  publishing  houses  who  have  extended 
courtesies  in  the  way  of  illustrations. 

F.  N.  P. 

Los  Angeles,  California. 


CONTENTS 


CHAPTER  I 
A  STUDY  OF  MATTER 21 

CHAPTER  II 
WATER  AND  HYDROGEN  PEROXIDE 34 

CHAPTER  III 
OXYGEN  AND  OZONE 51 

CHAPTER  IV 
HYDROGEN        63 

CHAPTER  V 

THE   ATMOSPHERE  72 


CHAPTER  VI 

GASES  AND  SOME  GAS  LAWS 84 

CHAPTER  VII 

SYMBOLS  AND  FORMULAS ,     .     .          ...     106 

CHAPTER  VIII 
SOME  CHEMICAL  PROBLEMS       112 

CHAPTER  IX 
THE   HALOGENS 119 

CHAPTER  X 
ACIDS  AND  BASES       136 

CHAPTER  XI 

NITROGEN  AND  COMPOUNDS       .....     145 

13 


14  CONTENTS 

CHAPTER  XII 
CARBON 159 

CHAPTER  XIII 
VALENCE 173 

CHAPTER  XIV 
ILLUMINATING  AND  FUKL  GASES 183 

CHAPTER  XV 
FLAME 189 

CHAPTER  XVI 
METHODS  OF  LIGHTING 197 

CHAPTER  XVII 
SOME    ORGANIC    COMPOUNDS 203 

CHAPTER  XVIII 
ETHEREAL  SALTS,  OILS,  FATS,  SUGARS 212 

CHAPTER  XIX 
FOODS  AND  THEIR  BODY  VALUES 224 

CHAPTER  XX 
SOLUTION  AND  IONIZATION 233 

CHAPTER  XXI 
SULPHUR  AND  COMPOUNDS 249 

CHAPTER  XXII 
PERIODIC  CLASSIFICATION  OF  ELEMENTS 265 

CHAPTER  XXIII 

THE  NITROGEN  FAMILY  274 


CONTENTS  15 

CHAPTER  XXIV 
COMPOUNDS  OF  SILICON 294 

CHAPTER  XXV 
THE  ALKALI  METALS 305 

CHAPTER  XXVI 
SOME  LEAVENING  AGENTS 327 

CHAPTER  XXVII 
THE  CALCIUM   FAMILY 336 

CHAPTER  XXVIII 

HARD  WATERS — METHODS  OF   SOFTENING       346 

CHAPTER  XXIX 
CLEANING  AND  POLISHING 353 

CHAPTER  XXX 
THE  COPPER  GROUP 362 

CHAPTER  XXXI 
THE  MAGNESIUM-  FAMILY 379 

CHAPTER  XXXII 

THE  ALUMINUM   FAMILY  392 


CHAPTER  XXXIII 
THE  LEAD  FAMILY 402 

CHAPTER  XXXIV 
THE  CHROMIUM  FAMILY       411 

CHAPTER  XXXV 
MANGANESE  AND  COMPOUNDS  416 


16  CONTENTS 

CHAPTER  XXXVI 
THE  IRON  GROUP 419 

CHAPTER  XXXVII 
THE  PLATINUM  AND  PALLADIUM  GROUPS 434 

REFERENCE    TABLES  AND   GLOSSARY 

REFERENCE  TABLES  AND  GLOSSARY  437 


ILLUSTRATIONS 

FIG.  PAGE 

1.  Abundance    of   certain   elements        20 

2.  Showing  the  "north"  end  of  a  magnetic  needle  being  at- 

tracted by  the   "south''  end  of  another 28 

3.  Wire  showing  the  anode  and  the  cathode 29 

4.  Electrolysis  or  Hoffmann  apparatus 37 

5.  Composition  of  water  by  weight 39 

(5.  Manometer  used  in  testing  gas  pressure 42 

7.  Diagrammatic  view  of  city  water  plant        46 

8.  Roosevelt  Dam,  which  is  very  similar  to  the  one  at   Sweet- 

water     .          47 

9.  Showing  relative  abundance  of  oxygen   in  nature     ...  52 

10.  Preparation   of    oxygen        53 

11.  Preparing  oxygen  from  sodium  peroxide 54 

12.  Boiling  water   in   paper   cup        57 

13.  Machine  for  making  ozone 59 

14.  Electromotive  series  of  metals  and  bar  magnet  with  iron 

filings  attached 65 

15.  Preparing  hydrogen  from  water  by  means  of  sodium     .     .  60 

16.  Preparation  of  hydrogen  from  acids 67 

37.  Oxyhydrogen  blowpipe     . 68 

18.  Lavoisier,    beheaded    in    French    Revolution,    the    Father 

of   Modern   Chemistry 70 

19.  Nodules  in  which  the  nitrogen-fixing  bacteria  live  on  the 

roots  of  a  bean 77 

?0.   Dewar  bulbs.      The   thermos   bottle   is  merely   different    in 

shape o     .     .     .     .  81 

21.  Comparison   of   thermometers 85 

22.  Aneroid  barometer 88 

23.  Illustrating  pressure  of  water  vapor 91 

24.  Contraction   of   volume   on   mixing   two    liquids     ....  94 

25.  Dalton,  who  proposed  the  atomic  theory  of  matter     ...  98 

26.  A  simple  eudiometer  connected   to   induction  coil     .     .     .  101 

27.  Preparation  of  chlorine  in  the  laboratory 121 

28.  Manufacture  of  chlorine 122 

29.  Effect  of  sunlight  on  chlorine  water 124 

I  17 


18  ILLUSTRATIONS 

TIG.  PAGE 

150.  Apparatus  for  purifying  iodine  by  sublimation     ....  132 
.'51.  Method  of   determining  approximately  the   proportion    of 

nitrogen  in  the  air 140 

32.  Manufacture  of  ice 149 

33.  Preparation  of  nitric  acid 152 

34.  Some  forms  of  smokeless  powder 15(5 

35.  Burning   of   a    diamond        1(51 

3(5,  Moissan's  electric  furnace .  162 

37.  Oil  derricks,  a  familiar  sight    in  oil-producing  sections     .  1C5 

38.  Formation  of  carbon  monoxide  in  a  furnace 169 

39.  Pouring  carbon  dioxide  upon  burning  candles  in  a  trough  172 

40.  Babcock  fire  extinguisher 174 

41.  Acetylene   burner         184 

42.  "Burning"  air       ..." 191 

43.  Match  suspended  within  burning  gas  jet 192 

44.  Burning  gas  drawn  from  center  of  candle  flame     ....  193 

45.  Determination  of  flash  point  of  an  oil 198 

46.  Starch  granules 221 

47.  Foods  rich  in  iron 231 

48.  Foods  rich  in  phosphorus     . 232 

49.  lonization  of  a  solution  of  common  salt,  and  proof  of  same  242 

50.  Method  of  obtaining  sulphur  in  Louisiana 250 

51.  Sulphur  crystals 251 

52.  Chamber  process  for  sulphuric  acid 261 

53.  Manufacture  of  phosphorus 276 

54.  Preparation  of  phosphine 279 

55.  Marsh 's  test  for  arsenic 283 

50.  A  scene  in  one  of  the  petrified  forests  in  Arizona     .     .     .  295 

57.  Mold  for  making  glass  tumblers 300 

58.  Mold  for  blowing  glass  bottles 301 

59.  Making  window  glass 302 

60.  Preparation  of  sodium  by  the  Oastner  process     ....  307 
01.  Preparation  of  salt  in  San  Francisco  Bay,  by  evaporation 

of  sea  water 310 

62.  Scale  in  iron  pipes,  from  an  actual  cnse 347 

63.  Making  an  electrotype 367 

64.  Hydraulic    mining 375 

65.  Manufacture  of  aluminum 394 

66.  Thermit  crucible,  sectional  view 395 


ILLUSTRATIONS  19 

FIG.  PAGE 

67.  A    thermit   crucible    ready    for    use    in    mending   a    broken 

casting- 396 

68.  A  thermit  crucible  in  operation,  mending  a  broken  casting  397 

69.  A  battery  " grid" 408 

70.  A  blast  furnace   for   preparing   cast   iron 421 

71.  A  blast  furnace,  showing  the  molds  for  the  "pigs"  in  the 

sand 423 

72.  The  Bessemer  converter  425 


APPLIED  CHEMISTRY 


CHAPTER  I 

A  STUDY  OF  MATTER 
Outline — 

Introduction 

Former  Method  of  Reasoning 

Present  Methods  of  Scientific  Investigation 

Old  Theories  of  Matter 

(a)   Composition  of 

(&)   Transmutation 
Present  Ideas 
Elements 
Compounds 

(a)   Definition  of 

(6)   Chemical  Union 

(c)  Method  of  Naming 

(d)  Explanation  of  Chemical  Union 
Chemical  Changes 

Kinds  and  Illustrations 
Mixtures 

1.  Introduction. — Nearly  every  normal  child  is  born 
an  interrogation  point.  Almost  as  soon  as  he  can  form 
sentences  be  begins  asking  "why;"  and  many  a  Christ- 
mas, toy  has  served  best  by  its  sacrifice  upon  the  altar 
of  childish  investigation  in  the  effort  to  learn  what 
makes  the  noise,  or  why  the  wheels  go  around.  The  his- 
tory of  the  child  is  largely  the  history  of  the  human  race. 
Were  the  spirit  of  inquiry  not  crushed  out  in  childhood, 
grown  to  youth  and  maturity,  all  would  still  find  the 
greatest  pleasure  in  studying  the  phenomena  of  nature. 
Some  few  survive  the  rebuffs  and  repressions  of  child- 

21 


22  APPLIED    CHEMISTRY 

hood  and  to  them  nature  ever  speaks  in  loving  and 
fascinating  words.  Others  must  have  this  instinct  of 
investigation  revived  in  their  hearts  if  they  find  pleas- 
ure in  axijyi  seienc^v  ; 

Chemistry , as 1 0,1? e,  branch  of  learning  probably  enters 
more1  largely lmfed  th&i  affairs  ,bf  ordinary  everyday  life 
than  any  other.  Without  it,  not  only  would  most  of  the 
great  engineering  achievements  of  the  world,  such  as 
the  construction  of  great  bridges  and  transcontinental 
railways,  and  the  Panama  Canal;  not  only  would  the  au- 
tomobile and  the  airplane  and  all  other  modern  means  of 
rapid  transportation  be  unknown,  but  the  many  little 
things  of  life  would  be  mysterious  and  unintelligible. 
Cookery  is  a  science  dependent  in  many  ways  upon 
chemistry ;  pure  foods  and  drinks  can  be  kept  so  only 
by  a  knowledge  of  chemistry;  healthful  air  and  sani- 
tary conditions  in  the  home  must  be  secured  by  a  knowl- 
edge of  chemistry  on  the  part  of  some  one.  Careful 
investigation  shows  that  a  knowledge  of  chemistry  must 
be  had  for  scientific  progress  in  almost  every  line  of 
human  activity.  This  little  book,  therefore,  will  seek 
to  be  helpful  in  furnishing  such  chemical  information 
as  shall  be  needed  in  the  affairs  of  the  home  and  in 
giving  added  interest  to  everyday  life ;  such,  that  these 
affairs  may  be  administered  the  more  wisely  and  that 
nature  may  speak  the  more  intelligibly;  such  that  those 
who  read  may  not  only  add  to  their  own  pleasures  but 
contribute  to  the  welfare  and  happiness  of  all  who  may 
come  under  their  influence. 

2.  Source  of  Scientific  Knowledge. — There  was  a  time 
in  the  world's  history  when  scientific  knowledge  was 
thought  possible  of  attainment  by  reasoning  alone.  Aris- 
totle, it  is  said,  maintained  that  a  vessel  filled  with  ashes 
or  sand  would  hold  as  much  water  as  if  there  were  nq 


A   STUDY    OF    MATTER  23 

ashes  or  sand  in  it.  He  never  made  the  experiment  to 
prove  or  disprove  the  truth  of  his  statement  and  such 
was  the  strength  of  his  influence,  and  such  the  method 
of  reasoning-  of  the  times  and  long  after,  that  centuries 
passed  before  anyone  sought  to  question  by  experiment 
the  truth  of  his  statement. 

3.  Present  Methods. — In  this  age  of  the  world  every 
statement   of   scientific   fact   or   supposed   fact   is   sub- 
mitted to  the   most  rigid   and   searching   examination; 
not  only  is  reason  applied,  but  every  possible  .method 
of  testing  experimentally  the  truth  of  the  statement  is 
used.     To  illustrate:     Some  years  ago  one  of  England's 
greatest  chemists  announced  in  a  paper  read  before  a 
scientific  gathering  that  he  had  succeeded  in  making  a 
certain  amount  of  lithium  from  copper  by  the  use  of 
radium.     The  next  morning's  sun  had  hardly  risen  be- 
fore many  of  his  hearers  were  preparing  to  repeat  his 
experiment,  not  for  the  sake  of  the  experiment,  but  to 
prove  or  disprove  his  claims.     So,  in  the  present  age  of 
the  world,   every  theory  of  every  scientist,  no  matter 
how  noted  he  may  be,  or  however  plausible  his  theory 
may  seem,  must  be  subjected  to  the  test  of  practical  ex- 
periment before  it  can  be  accepted  as  a  scientific  fact. 

4.  Some   Abandoned   Theories. — As    a   result    of   the 
manner  of  thought  of  centuries  ago,  many  theories  were 
accepted  as  sufficiently  plausible  which  long  since  have 
been  abandoned.    When  a  vessel  of  water  is  left  exposed 
to  the  air  or  placed  upon  some  source  of  heat,  the  water 
disappears.     Centuries  ago  it  was  believed  that  water 
upon  the  addition  of  heat  is  changed  into  air ;  further, 
that  the   air  upon  the  removal   of  the   heat   again  be- 
comes water.     This  was  based  upon  a  very  superficial 
observation,   first    the    disappearance    of   the   water   as 
stated,  and  second,  its  appearance  upon  the  surface  of 


24  APPLIED    CHEMISTRY 

any  cold  object  brought  into  a  warm  room,  as  upon 
the  outside  of  a  tumbler  of  ice  water.  But  no  careful 
experiments  were  ever  made  to  prove  or  disprove  the 
theory.  It  was  also  believed  that  when  water  is  boiled, 
a  portion  of  it  is  converted  into  an  earthy  substance. 
True,  upon  the  inside  of  the  tea-kettle  in  the  kitchen  a 
hard,  brittle  crust  gradually  forms,  but  this  is  simply 
mineral  matter  which  has  been  previously  dissolved  in 
the  water.  Pure  water  never  leaves  any  such  residue. 
But  the  old  philosophers  never  made  the  experiment 
with  pure  water,  as  they  might  have  done,  to  prove 
the  truth  of  their  position. 

5.  Transmutation, — At  the  time  chemistry  had  its 
birth,  philosophers  believed  thoroughly  in  the  possi- 
bility of  the  transmutation  of  one  substance  into  an- 
other. Just  as  they  maintained  that  water  could  be 
changed  into  earth  and  air,  and  air  into  water,  so  they 
believed  one  metal  could  be  transmuted  into  another. 
They  had  observed  some  things  that  to  them  seemed 
sufficient  evidence.  Often,  in  their  copper  mines  they 
had  noticed  that  the  iron  tools  left  standing  for  some 
time  in  the  water,  which  seeped  in,  became  reddish  in 
color  and  looked  as  if  the  iron  were  changing  to  cop- 
per. This  may  be  seen  by  putting  a  bright  nail  or 
knife  blade  into  a  solution  of  blue  vitriol  for  a  minute 
or  two.  A  deposit  of  copper  really  forms  upon  the 
iron,  but  it  may  be  shown  experimentally  that  the  two 
meta^  are  simply  being  exchanged  for  one  another 
and  that  the  iron  is  not  changing  into  copper.  They 
knew  also  a  process  for  making  brass  by  fusing  copper 
with  an  ore  of  zinc  which  they  called  cadmeia.  They 
recognized  there  were  vast  differences  between  brass  and 
gold,  yet  never  did  they  doubt  that  it  was  entirely  pos- 


A   STUDY    OF    MATTER  25 

sible  to  change  iron  into  copper  and  this  into  gold ;  in 
fact  they  strongly  believed  in  the  possibility  of  trans- 
muting any  metal  into  any  other  if  they  could  but 
learn  the  method. 

6.  Matter. — Matter  is  anything  which  occupies  space, 
and  may  be  visible  or  otherwise.     Thus,  air  is  matter 
just  as  much  as  is  water  or  wood  or  iron.     What  the 
real  composition  of  matter  is  has  long  been  one  of  the 
great   questions   of  man.     There   have   possibly   always 
been  those  who  believed  that  there  is  but  one  kind  of 
matter  in  all  the  world,  and  that  everything  we  knoAV 
is  simply  a  modified  form  of  this  one  kind.     On  the 
basis  of  such  a  theory  it  was  not  hard  to  believe  in 
the  transmutation  of  the  metals.     Others  claimed  there 
were    four    primary    substances, — earth,    air,    fire,    and 
water,  and  that  these  in  a  way  could  be  changed  from 
the  one  into  the  other. 

7.  Present  Theory. — Robert  Boyle,   sometimes   called 
the  Father  of  Physics  and  Chemistry,  who  was  born  in 
1626,  advanced  the  theory  that  there  is  a  large  number 
of  kinds  of  matter,  how  many  no  one  knows.     To  these 
primary  forms  he  gave  the  name  of  elements,  and  the 
truth  of  his  view  has  long  been  accepted  by  most  of 
the   scientific   world.     According   to    this   idea,   an   ele- 
ment is  a  substance  that  cannot  be  divided  into  two  or 
more  kinds  of  matter.     Thus  gold  is  believed  to  contain 
only  .gold  and  copper  nothing  but  copper.     At  present 
there   are   known   83   elements,   the   greater  portion   of 
which    exist    in    comparatively    small    quantities,    and 
most  of  which  have  been  discovered  since  the  beginning 
of  the  nineteenth  century.     Of  these,  eleven  are  gases, 
two   are   liquids,   and   the   others   solids.      Some   of   the 
rarer  may  on  more  careful  study  be  found  not  to  be 
elements,  while  others  as  yet  unknown  will  probably  be 


26  APPLIED    CHEMISTRY 

discovered.  It  is  estimated  that  two  elements,  oxygen 
and  silicon,  constitute  about  75  per  cent  of  all  the  mat- 
ter of  the  earth  and  seven  others  nearly  all  the  re- 
maining 25  per  cent.  Clark  gives  this  table: 

Per  cent 

Oxygen   49.98 

Silicon     25.30 

Aluminum    7.26 

Iron 5.08 

Calcium 3.51 

Magnesium 2.50 

Sodium   2.28 

Potassium    2.23 

Hydrogen   0.94 

The  same  facts  are  shown  more  graphically  in  Fig.  1. 


Oxygen    50  % 


SUicon  257. 


Fig.   1. — Abundance   of  certain   elements. 

8.  Compounds. — A  compound  is  a  substance  contain- 
ing  two   or   more   elements   chemically   united   and   in- 
variably in  the  same  proportion  by  weight.     The  most 
familiar  of  all  compounds  is  water,  which  consists  of 
two  elements,  hydrogen  and  oxygen,  always  in  the  pro- 
portion of  1  to  8.     Common  salt  is  another  compound 
containing  the  two  elements,  sodium  and  chlorine,   al- 
ways united  in  the  proportion  approximately  of  46  to 
71. 

9.  Chemical  Union  Defined. — In  defining  a  compound 
in  the  preceding  paragraph  the  expression,  chemically 
united,  was  used.     If  two  substances  are  mixed,  the  re- 
sulting product  will  partake  of  the  nature  of  each  in- 
gredient.    Two  white  substances  will  give  a  white  pro- 
duct, a  red  and  white  will  give  a  pink,  a  white  and  black 


A   STUDY    OF    MATTER  27 

a  gray.  But  if  two  substances  differing  from  each  other 
unite  chemically  the  product  formed  may  not  partake  of 
the  properties  of  either  even  to  the  slightest  extent,  and 
will  be  essentially  different.  To  illustrate:  Hydrogen 
and  oxygen  are  both  colorless  gases,  the  former  inflam- 
mable ;  the  latter  essential  for  life  and  ordinary  combus- 
tion. When  the  two  unite  chemically,  at  ordinary  tem- 
peratures, the  resulting  product  is  a  liquid,  which  is  not 
only  not  inflammable  but  will  even  extinguish  fire  and 
cannot  be  inhaled.  Sodium,  in  common  salt,  is  a  soft 
metal,  silvery  white  in  color,  which  upon  the  moistened 
hand  or  in  the  mouth  would  catch  fire  and  produce  most 
serious  burns.  Chlorine,  the  other  ingredient,  is  a  heavy 
yellow  gas,  terribly  destructive  of  life  if  inhaled  and 
used  with  frightful  results  in  the  late  great  war.  When 
these  two  unite  chemically  each  loses  its  properties,  and 
the  two  produce  an  entirely  new  substance,  not  only  not 
harmful,  in  ordinary  quantities,  but  even  regarded  as  an 
essential  in  the  animal  economy.  Likewise,  two  white 
substances,  uniting  chemically,  may  produce  a  brilliant 
red,  as  do  potassium  iodide  and  mercuric  chloride;  two 
gases  may  form  a  solid,  as  will  ammonia  and  hydrogen 
chloride ;  two  liquids  a  solid.  Many  of  these  in  great 
variety  will  be  taken  up  from  time  to  time  and  need 
not  be  emphasized  here. 

10.  General  Plan  of  Naming  Compounds. — A  few  gen- 
eral statements  as  to  IIOAV  compounds  are  named  will  be 
helpful  at  this  time.  In  the  early  days  of  chemistry 
no  plan  was  followed  in  naming  the  various  substances 
prepared.  As  a  result,  peculiar  and  fantastic  names  of 
very  familiar  things  have  come  down  to  us.  At  the 
present  time  so  vast  is  the  number  of  compounds  known 
—hundreds  of  thousands — that  some  very  definite  and 
systematic  method  is  necessary,  In  most  cases  as  soon 


28  APPLIED    CHEMISTRY 

as  a  chemist  hears  the  name  of  a  compound,  he  knows 
its  composition  even  though  it  may  be  one  not  familiar  to 
him.  Common  salt  is  chemically  known  as  sodium  chlo- 
ride, and  one  knows  immediately  that  it  consists  of  so- 
dium and  chlorine ;  if  the  name  ends  in  ide  the  compound 
contains  only  the  elements  mentioned,  which,  except  in 
a  few  cases,  are  but  two  in  number.  Thus,  mercuric 
chloride  contains  mercury  and  chlorine;  potassium  io- 
dide, potassium  and  iodine.  If  the  name  of  the  com- 
pound ends  injite,  with  few  exceptions  which  need  not 
be  mentioned  here,  the  compound  contains  oxygen,  in  ad- 
dition to  the  other  elements  named.  Thus,  sodium  chlo- 


Fig.    2. — Showing   the    "north"    end    of   a  magnetic    needle    being   attracted   by 
the   "south"   end   of   another. 

rate  contains  sodium,  chlorine  and  oxygen;  potassium 
sulphate,  potassium,  sulphur  and  oxygen. 

11.  What  Elements  will  Unite? — Not  every  element 
will  unite  with  every  other  element.  If  two  magnets, 
either  bar  or  horseshoe,  be  placed  together,  end  to  end, 
there  will  be  no  attraction  if  the  two  ends  marked  - 
are  brought  together  or  likewise  if  the  two  marked  + ; 
but  if  an  end  marked  -{-  be  brought  up  to  one  with  the 
opposite  sign  they  adhere  strongly.  This  is  always  true. 
Everyone  is  familiar  with  the  ordinary  compass,  often 
spoken  of  as  th.e  mariner's  compass.  If  the  end  of  the 


A    STUDY    OF    MATTER 


29 


needle  which  points  north  be  approached  by  the  north 
end  of  a  similar  magnetic  needle,  the  one  free  to  move 
will  swing  away;  if  the  opposite  end  be  approached  they 
will  attract  each  other.  (See  Fig.  2.)  From  these  facts  a 
simple  law  has  been  formulated:  "Like  poles  repel  and 
unlike  poles  attract  each  other. ' '  If  the  ends  of  two  wires 
connected  with  an  electric  battery  be  dipped  in  a  solution 
through  which  the  current  can  pass  in  a  U-shaped  tube 
as  shown  in  Fig.  3,  the  wire  upon  which  the  current 
enters  is  spoken  of  as  the  anode,  from  a  Greek  word 
meaning  the  road  in  and  the  wire  upon  which  the  current 
passes  out  is  called  the  cathode,  or  the  road  out.  Often  the 


Fig.   3. — The   wire   marked   +   is    the  anode   and   the   other  is   the   cathode. 

anode  is  called  the  positive  and  the  cathode  the  negative 
electrode.  Now  if  the  solution  used  be  one  of  common 
salt,  sodium  chloride,  it  will  be  found  that  the  sodium  al- 
ways collects  at  the  cathode  and  the  chlorine  at  the  anode. 
For  this  reason,  applying  the  law  stated  above,  sodium  is 
regarded  as  a  positive  element  and  chlorine  as  a  negative. 
In  general,  in  all  similar  compounds  the  metal  collects  at 
the  cathode  and  the  other  element  at  the  anode.  Hence, 
all  such  consist  of  a  positive  and  a  negative  element 
or  group  of  elements.  In  naming  such  compounds 
the  positive  is  always  given  first.  Thus,  sodium  chloride 
contains  a  positive  element,  sodium,  and  a  negative  ele- 


30  APPLIED  CHEMISTRY 

ment,  chlorine.  Copper  sulphate  contains  copper,  a  posi- 
tive element  and  a  negative  group,  consisting  of  sulphur 
and  oxygen.  It  would  seem  then  from  these  statements 
that  chemical  union  is  a  kind  of  electrical  attraction. 

12.  Chemical    Changes,    Kinds. — There    are    several 
kinds  of  chemical  changes;  in  all  cases  the  identity  and 
the  characteristics  of  the  substances  involved  are  lost  or 
destroyed.    This  has  been  illustrated  in  the  case  of  hydro- 
gen and  oxygen  uniting  to  form  water  and  of  sodium 
and  chlorine,  to  form  common  salt.    Such  as  these  are  very 
simple  and  are  known  as  "Additive  Reactions/'  an  expres- 
sion which  indicates  that  the  two  substances  have  been 
added  or  joined  together  and  have  formed  a  single  sub- 
stance.   Another  similar  and  very  familiar  case  is  that  o£ 
flashlight  powders  used  in  photography.    The  essential  in- 
gredient, that  which  produces  the  intensely  white  light, 
is  magnesium,   a  steel-gray  metal  which  has  been  pow- 
dered.   In  burning,  it  simply  combines  with  oxygen,  pro- 
ducing a  white  compound  known  as  magnesium  oxide, 
often   called   magnesia,   used   in   cleaning   felt  hats,   kid 
gloves,  as  a  dressing  for  white  shoes  and  for  similar  well- 
known  purposes. 

13.  Simple  Decomposition. — Another  kind  of  chemical 
change   equally   simple  as   the   preceding   is  known   as 
"Simple  Decomposition."     In  such  changes  the  process 
is  the  reverse  of  the  additive.    A  single  compound  by  heat 
or  some  other  force  is  decomposed  into  its  component  ele- 
ments.   To  illustrate  by  a  familiar  example,  mercuric  ox- 
ide, a  compound  whose  name  indicates  its  composition,  if 
heated  strongly  is  decomposed  into  mercury,  which  col- 
lects upon  the  sides  of  the  vessel  in  which  it  is  heated, 
and  oxygen,  which  is  invisible,  but  which  may  be  detected 
by  holding  a  pine  splinter  with  a  spark  upon  the  end 
above  in  the  outgoing  current  of  gas.     The  splinter  will 


A   STUDY    OP    MATTER  31 

burst  into  a  flame.  Likewise,  if  a  current  of  electricity 
be  passed  through  water  acidulated  to  render  it  a  conduc- 
tor, it  will  decompose  the  liquid  into  the  two  gases  of  which 
it  is  composed. 

14.  Metathesis,  or  Double  Decomposition. — By  far  the 
greater  number  of  chemical  changes  are  not  as  simple 
as  the  two  kinds  already  mentioned.     More  frequently 
two,  and  sometimes  more  than  two,  substances  unite  or 
react  with  each  other,  in  which  case  both  substances  are 
decomposed  and  two  or  more  new  ones  are  produced,  by  a 
rearrangement   of   the   elements   contained   in   the    com- 
pounds.   Such  a  change  is  spoken  of  as  "Metathesis"  or 
"Double  Decomposition."    It  may  be  illustrated  by  add- 
ing a  few  cubic  centimeters  of  a  solution  of  potassium  io- 
dide to  one  of  mercuric  chloride  in  a  test  tube.   Two  new 
substances  are  formed,  both  entirely  different  from  the 
original,  one  of  them  now  a  brilliant  red  color  and  not  sol- 
uble in  water.    Numerous   illustrations   of   this  kind   of 
change  will  be  had  from  time  to  time.  Really,  metathesis  is 
but  a  combination  of  the  other  two  kinds  of  change  in 
which  both  or  all  of  the  substances  used  are  decomposed 
and  the  products  combined  in  a  new  way. 

15.  Mixtures. — A  mixture  differs  from  a  compound  in 
that  the  composing  substances  do  not  unite  with  each  other 
as  in  additive  reactions;  neither  is  there  any  rearrang- 
ing of  the  elements  into  new  groupings.     Further,  as  a 
rule,  no  definite  amounts  of  the  two  substances  are  used, 
or  at  least  are  not  necessary.     The  particles  of  one  inter- 
mingle with  those  of  the  other,  but  each  retains  all  its 
own  properties.     White  sand  may  be  mixed  with  com- 
mon salt,  but  neither  has  lost  its  distinguishing  properties. 
A  little  placed  on  the  tongue  will  possess  a  salty  taste  and 
at  the  same  time  will  have  the  gritty  feeling  of  the  sand. 
Moreover,  one  may  readily  be  separated  from  the  other 


32  APPLIED    CHEMISTRY 

by  adding  water,  stirring  and  after  a  few  minutes  decant- 
ing or  filtering.  A  common  case  given  by  nearly  all  books 
is  that  of  fine  iron  filings  and  flowers  of  sulphur.  Mixed 
together,  the  result  is  a  greenish-gray  powder,  but  neither 
has  lost  its  distinguishing  properties,  and  as  in  the  case 
of  the  salt  and  sand  they  may  be  readily  separated. 
With  patience  most  of  the  iron  filings  may  be  successfully 
separated  from  the  sulphur  by  a  good  magnet.  An  easier 
and  more  satisfactory  method  is  to  add  carbon  disulphide 
which  upon  shaking  will  dissolve  the  sulphur  as  water  will 
salt.  The  dissolved  sulphur  may  then  be  poured  off 
through  a  filter  paper;  if  the  filings  are  washed  with 
another  portion  of  the  carbon  disulphide  all  the  sulphur 
may  be  removed.  By  evaporating  the  liquid  the  sulphur 
may  be  recovered  with  all  the  properties  it  possessed  be- 
fore. If,  however,  the  intimate  mixture  be  heated  for 
some  time  strongly  in  a  test  tube,  the  resulting  mass  will 
be  black  instead  of  greenish,  will  not  be  attracted  by  the 
magnet  as  the  filings  were,  and  the  sulphur  cannot  be  re- 
moved by  solution.  Chemical  union  has  taken  place  and 
we  now  have  a  compound  of  iron  and  sulphur,  called  iron 
sulphide. 

Exercises  for  Review 

1.  Do  you  believe  Aristotle's  statement  about  the  globe  of  sand? 
Give  reason  for  your  answer. 

2.  At  the  present   time  how  is   scientific   truth   obtained?     Can 
reason  aid  at  all  in  the  discovery  of  Nature's  laws?     Explain. 

3.  What  was  the   old   idea  regarding  the   relation   of   water  to 
air?    What  facts  had  they  to  cause  such  a  belief? 

4.  What  is  meant  by  transmutation?    What  led  the  ancient  phil- 
osophers to  believe  in  such  a  thing?     Do  you  believe  it  possible? 
Why? 

5.  What  is  matter?     How  many  kinds  can  you  find  in  this  book? 
In   this  room?      Give    two    old   theories   about   the   composition   of 
matter. 


A   STUDY    OF    MATTER  33 

6.  What  was  Boyle's  idea  of  matter?    What  is  the  present  idea? 
Is  this  necessarily  the  true  idea?     Explain. 

7.  Define  an  element.     How  many  are  known?     How  many  are 
liquids?     Solids?     How  many  constitute   nearly  the   whole   of   the 
earth?     What  two  are  the  most  abundant? 

8.  What  is  a  compound?     Name  two  and  give  composition.     Ex- 
plain what  is  meant  by  chemical  union.     Illustrate. 

9.  What  is  the  general  plan   of   naming  compounds?     Give  the 
signification  of  the  endings  ide  and  ate.     Give  illustrations. 

10.  Into  what   two   classes   are   elements    divided?     Will   copper 
and  silver  unite  to  form  a  compound?    Give  reason  for  your  answer. 

11.  How  can   one   learn   experimentally  whether   an  element  be- 
longs to  one  class  or  the  other?     Give  meaning  of  the  terms  anode 
and  cathode.     What  synonyms  are  sometimes  used? 

12.  Name  three  kinds  of  chemical  changes.     Give  illustration 
of  each.     Show  how  the  third  may  be  regarded  as  a  combination 
of  the   other   two. 

13.  How  does  a  mixture   differ  from  a  compound?     Name  two 
mixtures  and  give  some  easy  way  of  separating  them. 


CHAPTER  II 

WATER  AND  HYDROGEN  PEROXIDE 

Outline — 

Forms  of  Appearance 
Characteristics  of  Pure  Water 
Water  in  the  Human  Body  and  Foods 
Necessity  of  Water  to  the  Body 
Proof  of  Composition 

(«)   By  Electrolysis 
(&)   By  Weight 
Law  of  Definite  Proportions 
Water  of  Combination 

Hydrates 
Efflorescence 
Deliquescence 
Domestic  Water  Supplies 
City  Water  Supplies 
Hydrogen  Peroxide 
Law  of  Multiple  Proportions 

1.  Its  Familiarity. — Water  is  at  once  the  most  famil- 
iar of  all  natural  substances  and  one  of  the  most  inter- 
esting.    It  appears  in  a  very  large  variety  of  forms,  all 
more  or  less  familiar:  in  partially  condensed  vapor  as 
fog ;  in  the  feathery  cirrus  cloud ;  the  billowy  cumulus, 
the  beautiful  summer  cloud ;  the  stormy  and  threatening 
nimbus.    In  the  solid  form  as  snow,  hail,  ice,  glaciers  and 
icebergs. 

2.  Characteristics  of  Water. — Pure  water  is  tasteless, 
odorless  and  colorless,  except  in  great  depths  as  lakes 
and  seas,  when  it  appears  blue  or  bluish  green.     It  is 
often  said  that  distilled  water  tastes  flat,  but  this  is  be- 
cause we  are  accustomed  to  drinking  water  somewhat 
impure.     Just  as  beans  or  potatoes  or  other  vegetables 
served  without  salt  would  taste  flat  so  does  water  with- 

34 


WATER   AND    HYDROGEN    PEROXIDE  35 

out  the  usual  impurities.  Pure  water  when  evaporated 
leaves  no  residue,  hence  would  form  no  incrustation  on 
the  inside  of  kettles  or  boilers. 

3.  Water  in  the  Human  Body. — Not  only  does  water 
appear  in  such  variety  of  form  and  such  quantities  in 
nature,  but  it  constitutes  a  very  large  proportion  of  the 
animal  body.  Only  about  40  per  cent  of  the  human  body 
is  solid  matter,  while  in  the  lower  animals  the  percentage 
of  water  is  much  higher.  Our  foods  are  also  high  in 
water  content.  Even  butter  and  flour,  which  we  often 
think  of  as  dry,  contain  as  much  as  12  to  14  per  cent  of 
water  for  the  former,  and  10  to  11  for  the  latter.  The 
following  table  will  give  an  idea  as  to  many  of  the  com- 
mon food  products: 

TABLE 

Per  cent 

Beans,    dry    , 12.60 

Beans,    string    89.00 

Bread,    yeast     36.12-37.70 

Cabbage    91.50 

Carrots    88.20 

Cauliflower     . 92.30 

Celery   94.50 

Cheese 34.38-38.60 

Com,    dry    13.12 

Eggs    73.67 

Flour,    wheat     10.11 

Meat,  lean  beef   67.00-70.00 

Meat,    lean    pork 60.00 

Meat,    veal    73.30 

Mutton 50.20 

Oat    Meal    12.37 

•    Peas,    dry    12.62 

Peas,  green    79.93 

Potatoes,    sweet    75.00 

Potatoes,   white    66.10-80.60 

Rice 13.11 

Turnips     89.60 

Watermelons    .  ..92.40 


36  APPLIED    CHEMISTRY 

4.  Value  of  Water  to  Animals  and  Plants. — Nothing 
need  be  said  about  the  value  of  water  in  the  household. 
Life  itself  is  impossible  without  it,  to  say  nothing  of 
the  comfort  it  brings.  Digestion  is  merely  a  process  by 
which  solid  foods  are  made  soluble  that  they  may  be 
carried  through  the  blood  to  all  parts  of  the  body.  As 
water  is  the  most  nearly  universal  solvent  it  enters 
largely  into  the  process  of  digestion.  Assimilation  of 
food  is  impossible  in  the  absence  of  water;  and  not  only 
is  this  true,  but  most  of  the  waste  matter  of  the  body 
is  carried  away  dissolved  in  water  or  mixed  with  it  in 
large  amounts.  On  account  of  its  high  specific  heat,  that 
is,  a  given  amount  of  water  contains  more  heat  energy 
than  the  same  weight  of  any  other  liquid  at  the  same 
temperature,  it  is  regarded  as  the  best  means  of  warming 
houses  in  severe  weather.  It  is  this  very  fact  that  tempers 
the  winters  in  the  Great  Lake  regions  and  along  the 
oceans,  and  renders  the  climate  of  countries  washed  by 
the  Gulf  Stream  and  Japan  Current  far  warmer  than 
other  countries  in  the  same  latitude  not  thus  favored. 
In  the  human  body,  the  blood,  largely  water,  in  constant 
circulation,  tends  to  keep  the  body  of  perfectly  uniform 
temperature.  In  summer,  the  body  is  cooled  by  the  rapid 
evaporation  of  the  water  in  the  blood  through  the  pores 
of  the  skin;  thus,  summer  and  winter,  the  water  in  the 
body  serves  to  keep  a  uniform  temperature  throughout. 
To  maintain  the  supply  thus  needed,  an  ordinary  per- 
son requires  from  two  to  three  pints  of  water  per  day, 
in  summer  more  than  in  cold  weather.  Plants,  likewise, 
must  have  water  to  enable  them  to  absorb  the  necessary 
substances  of  food  value  from  the  soil,  as  also,  to  make 
the  cellulose,  starch  and  sugar,  which  they  store  up  in 
their  stems,  seeds  and  fruits. 


WATER   AND    HYDROGEN    PEROXIDE 


37 


5.  Composition  of  Water. — By  volume,  water  is  com- 
posed of  hydrogen,  two  parts,  and  oxygen,  one  part. 
This  is  usually  shown  experimentally  by  the  Hoffman 
apparatus  (Fig.  4).  K  is  a  reservoir  into  which  the 
water  is  poured  in  filling  the  apparatus.  It  is  neces- 
sary to  use  water  slightly  acidulated  with  some  acid,  as 
sulphuric,  since  pure  water  is  not  a  conductor  of  elec- 
tricity. In  filling  the  side  tubes,  B,  B,  the  stop-cocks  are 
carefully  opened,  one  at  a  time,  and  the  water  allowed 
to  flow  in  until  it  barely  reaches  the  stop-cock  level. 


Fig.    4. — Electrolysis    or    Hoffmann    apparatus. 

Not  much  more  should  be  put  into  R  than  will  fill  the 
three  tubes,  for  a  small  amount  of  water  makes  a  large 
quantity  of  gas  and  this  forces  the  excess  back  into  the 
reservoir,  hence  room  must  be  left  to  receive  it.  Plat- 
inum strips,  A,  A,  serve  as  electrodes  and  are  connected 
with  the  source  of  current  by  means  of  wires  sealed  in 
glass  tubes  passed  through  the  corks,  C,  C.  When  every- 
thing is  ready  the  current  is  turned  on ;  bubbles  imme- 
diately begin  to  rise  from  both  electrodes,  much  faster 
from  the  cathode  than  the  anode.  After  a  few  moments 


38  APPLIED    CHEMISTRY 

the  quantity  of  gas  in  each  tube  may  be  read  from  the 
graduations  etched  011  the  tubes,  B,  B.  It  will  be  found 
that  the  quantity  of  one  gas  is  always  double  that  of  the 
other.  To  know  that  the  smaller  volume  is  oxygen,  hold 
a  splinter  with  a  spark  on  the  end  over  the  tip  of  the 
tube  and  carefully  open  the  stopcock.  The  pressure  of 
the  water  in  R  will  force  the  gas  out  and  ignite  the 
splinter.  This  characteristic  test  for  oxygen  has  been 
mentioned  in  the  preceding  chapter.  The  usual  method 
of  testing  hydrogen  is  by  lighting  it.  A  burning  match 
or  better,  a  small  candle,  brought  to  the  tip  of  the  tube 
containing  the  larger  quantity  of  gas,  will  ignite  it  when 
the  stop  cock  is  cautiously  opened.  The  flame  at  first 
will  be  invisible,  or  until  the  glass  becomes  red-hot; 
but  a  piece  of  paper  held  to  it  will  be  instantly  ignited, 
thus  showing  the  presence  of  a  flame. 

6.  Explanation    of    the    Experiment. — Students    fre- 
quently ask  why  the  hydrogen  goes  to  the  cathode  or 
negative  electrode,  and  the  oxygen  to  the  anode.     This 
will  be  readily  understood  if  it  is  remembered  what  was 
said  in  the   preceding   chapter   about   compounds   con- 
sisting of  a  positive  and  a  negative  element  or  group. 
Since   oxygen   belongs   to   what   we   call   the    negative 
group,  it  would  necessarily  be  attracted  to  the  anode : 
while  hydrogen,  being  positive,  would  be  attracted  to 
the  negative  electrode. 

7.  Proof  of  Composition  by  Weight. — Since  gases  are 
very  light   substances   it   is   necessary   to   obtain   their 
weights  indirectly  in  this   experiment.     In  Fig.   5  hy- 
drogen  is    obtained    from    any    suitable    generator,    K, 
which  for  convenience  may  well  be  a  Kipp  apparatus. 
In  order  that  the  gas  may  be  perfectly  dry  it  is  allowed 
to    bubble    slowly   through   a    wash   bottle,    containing 
concentrated  sulphuric  acid,  which  is  an  excellent  dry- 


WATER   AND    HYDROGEN    PEROXIDE 


39 


ing  agent  in  that  it  absorbs  water  readily.  The  tube,  T, 
macb  of  hard  glass,  contains  copper  oxide,  preferably 
in  what  is  known  as  the  wire  form.  Before  connecting, 
this  tube  with  contents  is  carefully  weighed.  In  the 
U-tube  calcium  chloride  in  small  lumps  is  placed,  the 
tube  and  contents  carefully  weighed  and  connected  to 
the  combustion  tube  as  shown.  The  hydrogen  is  then 
turned  on,  the  heat  applied,  gently  at  first,  until  the 
glass  is  well  warmed,  and  the  operation  continued  until 
the  contents  of  C  have  become  red  like  bright  copper. 
The  heat  is  then  turned  off,  the  hydrogen  allowed  to 
flow  until  the  tube  is  cooled  enough  to  handle  comfort- 


Fig.   5. — Composition  of  water  by  weight. 

ably  when  both  T  and  U  with  contents  are  again  carefully 
weighed.  What  has  happened  is  as  follows:  Hydrogen 
has  the  power  of  taking  oxygen  away  from  many  oxides 
when  heated  strongly.  It  does  so  in  this  case  and  leaves 
in  the  combustion  tube  mostly  pure  copper.  The  loss 
of  weight  in  this  tube,  therefore,  is  the  weight  of  the 
oxygen  used.  The  hydrogen  and  oxygen  at  the  tem- 
perature present  combine  to  form  water,  which  in  the 
condition  of  vapor  passes  over  and  is  absorbed  by  the 
calcium  chloride  in  tube  U.  The  gain  here,  therefore, 
is  the  weight  of  the  water  produced.  Subtracting  the 
weight  of  the  oxygen  used  from  that  of  the  water  formed 


40  APPLIED    CHEMISTRY 

gives  the  weight  of  the  hydrogen.  Allowing  for  experi- 
mental errors  which  are  always  possible,  it  will  be  found 
that  the  average  of  a  large  number  of  experiments  car- 
ried out  thus  is  always  8  parts  of  oxygen  to  1  of  hy- 
drogen. A  typical  case  with  data  obtained  by  actual 
experiment  is  given  below: 

Copper  oxide  and  tube  before  heating 37.23  grams 

Weight  of  same,  after  heating 29.87 

Loss,   which   is    oxygen 7.36 

Calcium  chloride  and  tube,  before  heating.  .  .  .25.18 
Weight  of  same,  after  heating 33.46 

Gain,  which  is  the  water 8.28 

Subtracting  the  oxygen  from  weight  of  water  0.92 
Ratio  of  oxygen,  7.36,  to  hydrogen,  .92,  is  8  to  1 

8.  Law  of  Definite  Proportions. — It  was  stated  in  the 
preceding  chapter  that  a  compound  is  a  substance  con- 
taining two  or  more  elements  united  in  a  fixed  and  defi- 
nite proportion  by  weight.     The  above  experiment  il- 
lustrates  the    definition    and   at   the   same  itime    shows 
proof.    Out  of  this  truth,  which  applies  to  all  compounds, 
grows   the   "Law   of   Definite   Proportions,"    which    is 
usually  stated  thus:  When  two  or  more  elements  unite 
chemically  to  form  a  compound  they  always  do  so  in  the 
same  fixed  and  definite  proportion  ~by  weight.    Why  they 
must  necessarily  do  this  will  be  taken  up  at  another  time 
in  Chapter  VI. 

9.  Hydrates — Water  of  Combination. — All  have  seen 
various   substances   in   crystalline   form,    such   as   rock 
candy,  alum,  blue  vitriol,  or  such  natural  compounds  as 
iron  pyrite,  silica,  called  rock  crystal,  and  galena.   Crys- 
tals of  artificial  compounds  are  usually  prepared  by  dis- 
solving the  substance  in  water  and  allowing  the  water 
to  evaporate.    When  this  occurs,  very  often  a  consider- 
able portion  of  the  water  combines  with  the  dissolved 


WATER   AND    HYDROGEN    PEROXIDE  41 

solid  instead  of  passing  off  into  the  air.  Sometimes  the 
water  thus  combined  weighs  even  more  than  the  solid 
itself.  The  water  thus  taken  up  is  called  water  of  com- 
bination or  sometimes  water  of  crystallization,  and  the 
compound  thus  formed  is  called  a  hydrate.  Familiar  ex- 
amples of  hydrates  are  blue  vitriol,  Epsom  salts,  alum, 
sal  soda,  and  green  vitriol. 

TABLE  SHOWING  A  FEW  HYDRATES  AND  AMOUNT  OF  WATER 
Alum,    common.  .45.57  per  cent 

Blue  Vitriol 36.14 

Borax    47.12 

Epsom  salts 51.22  per  cent 

Green  Vitriol 45.32 

Sal    Soda 62.93 

10.  Efflorescence. — Hydrates  may  be  regarded  as  true 
compounds,  for  they  differ  greatly  in  their  physical 
properties  from  the  anhydrous  compound.  Thus,  ordi- 
nary hydrated  copper  sulphate  is  deep  blue  in  color,  and 
occurs  in.  more  or  less  regularly-shaped  triclinic  crys- 
tals. Anhydrous  copper  sulphate  is  white  in  color  and 
when  crystalline,  which  is  not  common,  is  in  slender 
needle-like  crystals.  However,  this  combination  is  rather 
an  unstable  one.  By  heat,  usually  the  water  of  the  hy- 
drate may  be  removed  without  affecting  the  composi- 
tion of  the  remaining  portion  of  the  compound  at  all. 
Even  at  ordinary  room  temperatures  in  many  cases  con- 
siderable portions  or  all  of  the  w^ater  of  combination 
spontaneously  passes  off  into  the  air.  The  extent  of  this 
loss  depends  upon  the  humidity  of  the  air,  the  tem- 
perature and  the  specific  rate  of  the  particular  compound 
itself.  This  may  be  seen  in  an  interesting  little  experi- 
ment. A  manometer  as  shown  in  Fig.  6  is  attached 
to  a  side-neck  test  tube.  A  bent  glass  tube  may  serve 
as  a  manometer  if  no  other  is  at  hand.  A  rubber  cork 


42 


APPLIED    CHEMISTRY 


is  fitted  snugly  into  the  test  tube  filled  about  half  full 
of  mercury.  The  bent  tube  also  contains  mercury  at  the 
same  level  in  both  arms.  A  crystal  of  some  hydrate, 
such  as  sodium  sulphate  is  put  upon  the  mercury  in  the 
test  tube  and  the  cork  carefully  inserted  again  so  as  not 
to  disturb  the  level  of  the  mercury  in  the  bent  tube,  M. 
Even  at  the  room  temperature  water  will  escape  from 
the  crystal,  producing  pressure  upon  the  mercury  in  the 
manometer,  moving  it  up  the  longer  arm,  until  there  is 


Fig.   6. — Manometer,   used  in  testing  gas   pressure. 

equilibrium.  At  this  point  no  more  water  escapes  from 
the  hydrate  on  account  of  the  pressure  exerted  upon 
it.  Now,  if  the  temperature  be  raised  a  few  degrees,  more 
water  will  be  expelled  and  the  mercury  will  rise  in  the 
outer  arm  still  higher,  until  the  added  pressure  again 
equals  the  vapor  pressure  of  the  water  in  the  crystal. 
Upon  cooling  the  equilibrium  is  again  disturbed  and 
through  the  pressure  of  the  mercury  the  hydrate  will  ab- 
sorb water  vapor  until  there  is  again  equal  pressure  within 
and  without  the  hydrate.  In  the  open  air,  as  the  pres- 
sure is  not  increased  by  the  escape  of  the  water,  the  loss 


WATER   AND    HYDROGEN    PEROXIDE  43 

continues  until  no  more  can  be  driven  off  at  that  tem- 
perature. A  considerable  number  of  hydrates  are  able 
to  part  with  all  their  water  at  ordinary  room  tempera- 
ture and  usual  atmospheric  conditions.  Such  hydrates 
are  said  to  be  efflorescent.  Efflorescence  may  be  denned 
as  the  property  which  some  hydrates  possess  of  giving 
off  to  the  air  their  water  of  combination  and  of  crumb- 
ling to  a  powder.  The  word,  literally  translated,  means 
becoming  flowers  or  flour,  that  is,  a  fine  powder.  When 
efflorescence  occurs,  the  crystalline  structure  of  the  sub- 
stance is  destroyed  and  usually  a  powder  results.  Such 
hydrates  as  sal  soda,  often  called  washing  soda,  ferrous 
sulphate,  and  Glauber's  salt,  or  sodium  sulphate,  are  ex- 
cellent examples  of  efflorescent  hydrates. 

11.  Deliquescence. — Deliquescence  may  be  defined  as 
the  property  some  substances  have  of  attracting  mois- 
ture from  the  air  in  such  quantities  as  to  be  dissolved 
in  it.  The  word  means  becoming  liquid.  Two  such  sub- 
stances have  been  mentioned  already,  used  in  the  experi- 
ment for  the  determination  of  the  composition  of  water 
by  weight,  sulphuric  acid  and  calcium  chloride.  They 
have  frequent  applications  in  the  chemical  laboratory  for 
drying  gases.  As  calcium  chloride  is  a  by-product  of  cer- 
tain industries  and  very  cheap,  it  has  been  tried  by  the 
United  States  government  experimentally  as  a  preventive 
of  dust  on  roadways,  instead  of  frequent  sprinkling.  Ob- 
viously it  could  not  be  used  thus  where  there  is  much 
rain  in  the  summer  season,  since,  on  account  of  its  great 
solubility,  it  would  be  quickly  washed  away.  Other  good 
examples  of  deliquescent  substances  are  caustic  soda,  of- 
ten called  lye,  and  caustic  potash.  A  hygroscopic  sub- 
stance is  one  that  will  in  damp  weather  absorb  moisture 
from  the  air  in  sufficient  quantities  to  become  moist  but 
not  to  liquefy.  For  example,  common  salt  in  our  homes 


44  APPLIED    CHEMISTRY 

often  becomes  damp  in  rainy  weather  but  it  never  lique- 
fies, hence  is  hygroscopic  rather  than  deliquescent. 
Keally,  however,  in  this  case  the  condition  is  due  to  the 
presence  of  a  small  quantity  of  a  deliquescent  substance, 
such  as  magnesium  chloride,  and  not  to  the  salt  itself  be- 
ing hygroscopic. 

12.  Domestic   Water   Supplies. — Water   is   the   most 
nearly  universal  solvent  known.     Glass,  rocks  and  min- 
erals of  all  sorts,  which  ordinarily  are  thought  of  as  in- 
soluble in  water,  when  left  for  long  periods  in  contact 
with  water,  do  dissolve  appreciably.     This  is  the  source 
of   all   mineral   and   hard   waters.      Organic   impurities 
likewise   and  substances  of  all   sorts   are   dissolved  by 
water,   so   that   especially  in  towns   and   cities,   but   in 
reality  everywhere,  the  domestic  supply  of  water  must 
be   carefully  guarded.     Cisterns,  springs  and  wells  in 
large  towns  and  cities  are  never  safe,  and  frequently 
not  in  smaller  places.     Sewage  and  seepage  from  cess 
pools    make    their   way   through    the    soil    to    all    such 
sources  of  water  and  cause  serious  contamination.    The 
water  may  be  perfectly  clear  and  tasteless,  yet  abso- 
lutely unfit  to  drink.     Only  chemical  and  bacteriologic 
tests  can  show  and  in  case  of  doubt  these  should  be 
applied. 

13.  Rivers  as  a  Source  of  Supply. — Probably  more  of 
the  large  American  cities   obtain  their  water  supplies 
from  rivers  than  from  any  other  source.    It  would  seem 
at  first  thought  that  such  would  be  open  to  the  greatest 
objection,  because  of  the  fact  that  they  are  the  common 
means  used  by  cities  in  disposing  of  their  sewage,  and 
are  accessible  to  contamination  in  various  ways.     For- 
tunately, however,  nature  has  a  method  of  destroying 
such    impurities.      Exposure    to    the    air    in    a    flowing 
stream,  especially  if  the  bed  be  rocky  so  as  to  cause  an 


WATER   AND    HYDROGEN    PEROXIDE  45 

agitation  of  the  water  and  to  bring  all  portions  of  it 
to  the  surface,  soon  results  in  the  destruction  of  most 
organic  impurities.  The  city  of  Los  Angeles  obtains 
its  water  supply  from  the  Owens  River,  bringing  it  over 
two  hundred  miles.  When  it  enters  the  upper  end  of 
the  San  Fernando  valley  it  dashes  rapidly  down  in  an 
open  viaduct  over  a  very  rocky  artificial  bed,  such  that 
the  water  is  churned  into  a  foam,  thoroughly  impreg- 
nating it  with  air.  A  very  noted  case  was  brought  to 
the  attention  of  the  public  a  feAv  years  ago  when  St. 
Louis  brought  suit  in  the  courts  against  Chicago  on 
the  grounds  that  the  latter  city  was  contaminating  the 
water  supply  of  the  former  by  conveying  vast  quantities 
of  sewage  through  the  Illinois  River  into  the  Mississippi 
not  far  above  the  intake  of  the  St.  Louis  supply.  Nu- 
merous analyses  of  the  water  were  made,  but  bacteri- 
ologic  and  chemical  tests  failed  to  sustain  St.  Louis  in 
her  claims.  Nevertheless,  pathologic  bacteria  are  able 
to  withstand  long  exposure  of  this  character  and  daily 
tests  of  city  water  must  be  made.  If  the  water  be 
muddy,  as  it  may  be  more  or  less  all  the  time,  and  very 
much  so  at  certain  seasons,  further  purification  is  nec- 
essary. Briefly  stated,  the  steps  are  about  as  follows: 
The  river  water  is  pumped  into  huge  basins  or  reservoirs, 
where  a  stream  of  lime  water  and  another  of  a  solution 
of  alum  or  some  other  coagulant,  are  allowed  to  enter 
through  pipes.  These  two  solutions  in  meeting  produce 
a  coagulum  or  gelatinous  precipitate  which  in  settling 
carries  practically  all  the  mud  with  it.  Naturally,  as  most 
of  the  bacteria  present  are  attached  to  mud  particles,  they 
are  carried  down  also.  At  intervals  this  accumulated 
deposit  is  washed  back  into  the  river.  In  very  large  cities, 
such  treatment  is  usually  supplemented  by  nitration  ba- 
sins from  which  the  water  passes  out  through  thick  layers 


46 


APPLIED    CHEMISTRY 


of  sand  and  gravel  as  is  shown  in  Fig.  7.  Finally,  before 
the  water  begins  its  journey  to  the  mains  of  the  city, 
either  liquid  chlorine  or  a  solution  of  bleaching  powder  in 
small  quantities  is  introduced  for  the  purpose  of  destroy- 
ing any  pathologic  bacteria  which  may  remain. 

14.  Lakes  as  a  Source  of  Supply. — Many  cities  obtain 
their  supply  from  lakes  either  natural  or  artificial.  In 
such  cases,  unless  the  lake  be  large  such  as  those  upon 
which  Chicago,  Cleveland  and  other  northern  cities  are 
located,  another  serious  problem  is  confronted.  A  cer- 


Fig.  7. — Diagrammatic  view  of  city  water  plant.  B,  the  settling  basin;  F, 
the  filter,  in  the  bottom  of  which  are  layers  of  sand  and  gravel,  indicated  by 
the  letters  5*  and  G. 

tain  kind  of  algae,  a  species  of  plant  to  which  the  com- 
mon green  scum  seen  upon  stagnant  ponds  belongs, 
grows  in  the  water  and  late  in  summer  produces  spores 
which  upon  bursting  liberate  a  very  offensive  odor,  so 
that  the  water  cannot  be  used  for  drinking  or  cooking. 
It  has  been  found  that  the  presence  of  a  minute  quantity 
of  some  copper  compound,  as  blue  vitriol,  will  prevent 
the  growth  of  such  algae.  Accordingly,  a  burlap  sack, 
filled  with  blue  vitriol  crystals,  is  suspended  from  a 


WATER    AND    HYDROGEN    PEROXIDE  47 

boat  and  is  rowed  back  and  forth  across  the  lake  in  ev- 
ery direction  for  hours  or  days,  until  the  copper  com- 
pound is  dissolved.  The  amount  of  blue  vitriol  present 
is  so  small  as  to  have  no  appreciable  effect  upon  the 
human  system,  but  is  destructive  to  the  algae.  By  some 
it  is  thought  that  the  copper  enters  into  combination 
with  the  albumin  of  the  alga3  and  settles  to  the  bottom. 
If  this  be  the  explanation,  then  there  is  none  left  in  the 


Fig.  8. — Roosevelt  Dam,   which  is  very  similar  to  the  one  at   Sweetwater. 

water.  There  are  several  cities  of  the  southern  states 
which  have  had  to  adopt  this  plan;  but  one  of  the 
most  noted  is  that  of  Sweetwater  Dam  a  few  miles  from 
National  City  and  San  Diego  in  southern  California. 
It.  is  a  huge  reservoir  in  a  mountain  valley,  formed  by 
a  concrete  dam  and  holds  fit  its  capacity  several  billion 
gallons  of  water.  See  Fig.  8,  a  typical  dam  for  such 
water  systems. 


48  APPLIED    CHEMISTRY 

HYDROGEN  PEROXIDE 

15.  Composition. — In  composition,  hydrogen  peroxide, 
or  dioxide,  as  it  is  often  called,  closely  resembles  water. 
Instead  of  having  eight  parts  of  oxygen  to  one  of  hy- 
drogen, as  is  the  case  with  water,  it  has  sixteen  of  oxy- 
gen to  one  of  hydrogen.    This  added  amount,  however,  is 
held  very  loosely,  much  as  is  true  of  the  water  contained 
by  many  hydrates.    As  a  result,  therefore,  it  is  escaping 
at   all   times,   unless   in   tightly   corked   bottles,   which 
should  be  kept  in  a  cool  place.    Even  then  the  oxygen  es- 
capes until  sufficient  pressure  is  attained  in  the  bottle 
to  produce  equilibrium  between  the  vapor  tending  to 
escape  from  combination  and  that  of  the  air  above.    This 
explains  why  the  cork  comes  out  with  a  "pop"  when  it 
has  not  been  previously  removed  for  some  time.     Hy- 
drogen peroxide  is  put  on  the  market  in  the  form  of  a 
weak  solution,  usually  about  3  per  cent,  not  only  under 
the  name  of  hydrogen  dioxide  but  also  as  dioxygen. 

16.  Uses. — The  value  of  dioxygen  as  an  antiseptic  de- 
pends upon  the  oxygen  being  continually  liberated.    Just 
as  flowing  water  is  purified  by  the  oxygen  of  the  air, 
so  bacteria  in  wounds  and  diseased  portions  of  the  body 
are  destroyed  by  this  more  concentrated  or  more  active 
oxygen.     It  will  be  observed  that  when  this  additional 
amount  of  oxygen  is  removed  from  the  dioxide,  only 
water  remains,  which  cannot  cause  irritation.     Hence, 
hydrogen  peroxide  is  probably  the  safest  as  well  as  one 
of  the  most  efficient  germicides  for  general  use.     It  is 
also  a  good  bleaching  agent  and  is  employed  successfully 
for  silks,  wool,  ivory,  feathers  and  hair,  animal  prod- 
ucts which  would  be  seriously  injured  by  more  power- 
ful agents  such  as  chlorine. 


WATER  AND   HYDROGEN   PEROXIDE  40 

17.  Method  of  Testing. — The  usual  method  of  testing 
a  solution  of  hydrogen  peroxide  is  by  adding  a  few  drops 
of  it  to  some  starch  mucilage  or  very  thin  paste  to  which 
has  previously  been  added   a   very   small   quantity   of 
potassium   iodide   solution.     A   deep    blue    solution   re- 
sults.    Another  sensitive  test  is  to  add  some  potassium 
dichromate  solution  to  one  of  hydrogen  peroxide  acid- 
ulated slightly  with  sulphuric  acid.     A  deep  blue  color 
forms  which  lasts  but  a  moment.     It  is  not  known  what 
this  blue  substance  is,  because  its  temporary  character 
prevents  any  examination  of  it.    If  some  ether  be  added 
before   putting   the   peroxide   into   the   dichromate   the 
deep  blue  compound  is  more  permanent;  by  shaking,  the 
ether  layer  may  be  made  to  take  up  most  of  the  color, 
so  that  the  test  is  thus  intensified. 

18.  Law  of  Multiple  Proportions. — It  has  been  seen 
that  the  composition  of  water  is  oxygen,  eight  parts, 
hydrogen  one ;  hydrogen  peroxide,  oxygen,  sixteen,  hy- 
drogen one.     Thus   two   elements,  uniting  in   different 
proportions,  form  two  different  compounds.     In  doing 
so,  for  a  certain  fixed  amount  of  hydrogen  the  oxygen 
is  twice  as  much  in  one  case  as  the  other,  that  is,  it 
varies  in  a  simple   ratio.     This  has  been  found  to   be 
generally    true    and    in    chemical    union    for    a    fixed 
amount  of  one  element,  the  other  will  always  unite  in 
some  simple  ratio  as  1:2,  1:3,  and  the  like.     Dalton  for- 
mulated this  in  what  is  known  as  the  "Law  of  Multiple 
Proportions."     Briefly  stated  it  is,  When  two  or  more 
substances  unite  in  different  proportions  to  produce  two 
or  more  different  compounds,  for  a  fixed  amount  of  one, 
the  varying  quantities  of  the  oilier  will  always  bear  some 
simple  ratio  to  each  other.     Later,  reasons  will  bo  seen 
why  this  must  necessarily  bo  so,  as  was  the  case  in  the 
law  of  definite  proportions. 


50  APPLIED   CHEMISTRY 

Exercises  for  Review 

1.  Name  six  different  forms  in  which  water  occurs. 

2.  Give   the   characteristics   of  pure   water.     Why   does  it   taste 
"flat"? 

3.  Give  some  idea  as  to  the  amount  of  water  in  the  human  body; 
also  in  many  of  our  food  products. 

4.  Explain  how  water   aids  in   digestion  and  assimilation;    also 
how  it  aids  in  warming  the   body   and  equalizing  temperature   in 
summer. 

5.  Describe  the  experiment  showing  analytic  proof  for  composi- 
tion of  water.     Explain  why  the  oxygen  collects  at  the  anode. 

6.  Outline  the  experiment  for  proof  of  composition  of  water  by 
\v  eight. 

7.  State  the  "Law  of  Definite  Proportions."     Illustrate. 

8.  What  jt  a  hydrate?     Water  of  combination?     Give  examples 
of  hydrates. 

9.  Define   efflorescence.     What  is  the   cause   of   it?     What   is  a 
manometer?      Give    some    experiment    using   a   manometer    and    its 
purpose. 

10.  Define    deliquescence.      Name    four    deliquescent    compounds. 
What  use? 

11.  What  is  a  hygroscopic  substance?     Why  does  salt  become 
damp  in  wet  weather? 

12.  How   do   cisterns   and   wells   become   contaminated?     Why 
are  rivers  apt  to  be  purer  than  cisterns  in  a  city?     How  are  river 
waters  clarified? 

13.  What   often   occurs   in  small  lakes  used   for   water   supply? 
How  treated? 

14.  Compare  water  and  hydrogen  peroxide.     Give  uses  of  latter. 

15.  Give  method  of  testing  hydrogen  peroxide. 

16.  State  "Law  of  Multiple  Proportions."     Illustrate. 


CHAPTER  III 

OXYGEN  AND  OZONE 

Outline — 

Abundance  of  Oxygen  in  Nature 
Preparation  in  Laboratory 

Catalysis 
Characteristics 

(«)   Physical 

(fc)    Chemical 
Uses  of  Oxygen 

(«)   Respiration 

(6)   Combustion 

(<")    Medical  and  Others 
Oxidation,   Combustion,   Explosion 
Ozone,  its  Relation  to  Oxygen 
Preparation  of  Ozone 

(rt)   In  Laboratory 

(&)    For  Commerce 
Characteristics 

(rt)    Physical 

(/;)   Chemical 
Uses 

1.  Abundance  of  Oxygen. — Oxygen  constitutes  about 
50  per  cent   of  all  terrestrial   matter.     Of  water  it   is 
eight-ninths  by  weight ;  of  the  rocky  crust  of  the  earth, 
such  as  limestone,  sand,  sandstone,  it  is  practically  50 
per  cent;  of  the  air  about  23  per  cent  by  weight;  of  the 
human  body  about  two-thirds.     Thus  it   is  by  far  the 
most  abundant  of  all  the  elements.    Fig.  9  gives  approx- 
imately the  relative  amount  of  oxygen  and  the  seven 
other  elements  which  constitute  the  greater  part  of  the 
material  of  the  earth. 

2.  Preparation. — As  far  as  known,  Scheele,  a  Swedish 
chemist,  first  prepared  oxygen  about  1773,  using  man- 

~A 


52  APPLIED    CHEMISTRY 

ganese  dioxide  and  sulphuric  acid.  However,  he  did  not 
publish  any  account  of  his  experiments  for  several 
years,  and  in  the  meantime  Joseph  Priestley,  an  English 
chemist,  had  in  August,  1774,  prepared  and  studied 
oxygen,  making  it  by  heating  red  mercuric  oxide.  It  is 
interesting  to  know  that  he  used  as  his  source  of  heat 
a  large  lens  or  burning  glass  to  concentrate  the  sun's 
rays  and  instead  of  the  modern  test  tube  he  had  a  sawed- 
off  gun  barrel.  Both  of  the  above  methods  are  still 
sometimes  used,  but  there  are  much  better  ways.  The 
most  common  method  for  obtaining  oxygen  in  the  labo- 
ratory is  by  heating  potassium  chlorate,  mixed  with 
manganese  dioxide.  The  first  named  compound  fur- 
nishes all  the  oxygen,  although  both  contain  it,  but 


Oxygen    50% 


Silicon  25% 


Fig.    9. — Showing    relative    abundance    of    oxygen    in    nature. 

much  less  heat  and  time  are  needed  if  the  mixture  is 
used.  By  putting  equal  amounts  of  potassium  chlorate 
into  each  of  two  test  tubes  and  adding  to  one  a  small 
quantity  of  manganese  dioxide,  it  is  interesting  to  note 
that  the  mixture  will  give  the  oxygen  test  at  the  mouth 
of  the  tube  in  from  one-sixth  to  one-fourth  the  time  that 
is  required  for  the  other.  Chemical  tests  show  that  the 
manganese  dioxide  is  unchanged  and  may  easily  be  recov- 
ered from  the  remaining  mixture  and  used  again.  The  ac- 
tion of  any  substance  in  thus  hastening  a  chemical  change 
is  called  catalysis,  and  the  agent  itself  a  catalyst  or  a 
catalytic  agent.  Many  such  cases  will  be  observed  from 
time  to  time  in  our  study  of  chemical  reactions.  For  exam- 
ple, it  has  been  stated  that  hydrogen  peroxide  is  a  very 
unstable  compound  and  owes  its  value  to  the  fact  of  giving 


OXYGEN    AND    OZONE 


53 


off  oxygen  so  readily.  The  addition  of  powdered  metals 
or  of  charcoal,  even  in  weak  solutions,  causes  rapid  decom- 
position of  the  peroxide.  In  a  polished  platinum  dish  a 
concentrated  solution  shows  little  evolution  of  oxygen, 
even  at  temperatures  considerably  above  that  of  the  or- 
dinary room ;  but  if  the  dish  be  roughened  or  scratched 
the  decomposition  becomes  rapid.  In  all  these  cases,  the 
powdered  metals,  the  charcoal  and  the  roughened  plat- 
inum serve  as  catalytic  agents  in  hastening  the  decom- 
position. 


Fig.    10. — Preparation    of   oxygen. 

The  laboratory  method  of  setting  up  the  apparatus  and 
of  collecting  the  gas  is  shown  in  Fig.  10.  The  method  is 
called  collecting  over  water,  and  all  gases  not  soluble  in 
water  may  be  collected  in  this  manner.  One  precaution 
must  be  rigidly  observed  and  that  is,  to  remove  the  deliv- 
ery tube  from  the  water  before  taking  the  heat  away  from 
the  generator.  A  third  method  often  used  when  only 
small  quantities  are  wanted  is  by  allowing  water  to  drop 
slowly  upon  sodium  peroxide,  a  compound  sold  under  the 


54 


APPLIED    CHEMISTRY 


name  of  "oxone."    It  gives  off  oxygen  on  the  addition  of 
water  just  as  does  hydrogen  peroxide  spontaneously. 

3.  Characteristics  of  Oxygen. — Physical. — Oxygen  is 
an  odorless  gas,  slightly  heavier  than  air,  and  in  small 
quantities,  is  colorless.  When  liquefied,  as  it  may  be  at 
182°  C.  below  zero,  it  is  of  a  distinctly  blue  color.  It  is 
possible  that  what  we  speak  of  as  the  blue  sky  may  be  the 
color,  at  least  in  part,  of  the  great  depth  of  oxygen.  It 
is  soluble  in  water ;  at  20°  C.,  to  the  extent  of  3  c.c.  in  100, 
and  in  ice  water  about  4  c.c.  in  100.  In  the  liquid  form 


Fig.    11.— Preparing   oxygen   from   sodium   peroxide. 

it  is  distinctly  magnetic,  as  is  shown  by  a  suspended  test 
tube  of  it  being  strongly  attracted  by  a  magnet.  It  may  be 
solidified  by  surrounding  with  liquid  hydrogen  and  is  then 
a  pale  blue  solid. 

Chemical  Characteristics. — The  most  important  chemi- 
cal property  of  oxygen  is  the  vigor  with  which  it  com- 
bines with  a  large  number  of  other  elements,  forming 
oxides.  Charcoal,  heated  to  redness,  and  lowered  into 
a  bottle  of  oxygen,  glows  brightly  and  if  made  from  soft 
wood,  it  bursts  into  sparks.  Phosphorus,  ignited,  in 


OXYGEN    AND    OZONE  55 

a  deflagrating'  spoon,  in  oxygen  burns  with  dazzling 
brightness,  while  iron  in  the  form  of  wire  or  a  watch 
spring  burns  with  a  beautiful  shower  of  sparks.  Sulphur 
and  zinc  both  burn  much  brighter  than  in  the  air.  All 
of  these  are  additive  reactions  in  which  oxygen  has  com- 
bined with  another  element  forming  an  oxide.  Usually 
upon  the  sides  of  the  bottle,  in  which  the  watch  spring 
is  burned,  will  be  seen  a  reddish  deposit  of  iron  oxide,  like 
rust,  but  most  of  the  iron  has  been  converted  into  what  is 
called  magnetic  oxide  and  has  dropped  to  the  bottom  of 
the  bottle  in  the  molten  condition.  The  charcoal,  being 
largely  carbon,  has  produced  carbon  dioxide,  and  so  on. 
Many  of  the  oxides,  like  the  one  formed  from  sulphur, 
when  dissolved  in  water  give  an  acid  test,  and  this  fact 
gave  oxygen  its  name,  from  the  Greek  words  meaning 
acid  former. 

4.  Uses. — First  of  all  should  be  mentioned  its  need  in 
respiration.  Aquatic  animals  breathe  the  small  quantity 
of  free  oxygen  dissolved  in  water,  while  land  animals 
use  the  more  concentrated  form  found  in  the  air.  Next 
to  its  value  in  respiration  is  its  use  in  combustion.  Or- 
dinary fire  is  impossible  without  oxygen ;  and  without 
fire  man  must  have  remained  little  more  than  a  savage. 
II?  could  hardly  have  passed  the  advancement  of  the 
stone  age;  the  reduction  of  metals  from  their  ores;  the 
making  of  steel  tools;  the  locomotive,  the  steamship,  the 
automobile,  the  airplane,  all  would  have  remained  for- 
ever beyond  him.  Besides  these  two  great  uses  there 
are  many  minor  ones.  The  oxygen  helmet  is  often  used 
by  firemen  to  enter  places  impossible  otherwise ;  by  div- 
ers in  exploring  sunken  vessels  and  for  other  under- 
sea work  ;  by  rescuers  after  explosions  in  mines.  The 
pulmotor  is  now  a  common  appliance  in  the  hospital, 
for  inducing  artificial  respiration  at  critical  times,  such 


56  APPLIED    CHEMISTRY 

as  cases  of  asphyxiation,   drowning,   electric   shock,   and 
in  crises  of  some  diseases. 

5.  Oxidation. — The  uniting  of  oxygen  with  any  sub- 
stance is  called  oxidation,  although,  in  the  broadest 
sense,  to  the  chemist  the  term  means  much  more  than 
this.  The  action  may  be  slow,  or  so  rapid  as  to  be  ac- 
companied by  the  generation  of  much  heat.  If  suffi- 
ciently rapid  to  cause  noticeable  heat  and  light  it  is 
called  combustion,  but  we  shall  see  that  combustion  often 
takes  place  between  substances  when  neither  one  is  oxy- 
gen. Some  substances,  for  example,  oily  waste  or  rags, 
absorb  oxygen  from  the  air:  oxidation  begins,  and  often 
sufficient  heat  is  produced  to  ignite  the  rags.  This  is 
spontaneous  combustion.  It  is  never  safe,  therefore,  to 
leave  waste  saturated  with  oils,  especially  drying  oils  like 
linseed,  exposed  long  to  the  air.  The  manufacturers  of 
the  familiar  cedar  mop  and  others  of  like  character,  who 
use  some  kind  of  oil  upon  the  cotton  thread,  provide  a 
metal  box  to  enclose  the  mop  when  not  in  use.  At  al- 
most every  coal  mine,  the  dump  is  seen  to  be  on  fire.  Cer- 
tain iron  compounds,  when  wet  by  rains  and  exposed  to 
the  air,  begin  to  oxidize ;  the  temperature  rises  and  even- 
tually is  sufficiently  high  to  ignite  the  small  quantities 
of  coal  thrown  out  with  the  waste  material.  The  fires 
in  coal  bins  on  shipboard  probably  often  occur  in  the 
same  way.  A  simple  experiment  illustrating  spontaneous 
combustion  may  be  made  by  dissolving  a  piece  of  yellow 
phosphorus  the  size  of  a  pea  in  a  cubic  centimeter  of  car- 
bon disulphide  and  pouring  the  solution  on  a  filter  paper 
resting  upon  a  ring  stand.  As  soon  as  the  carbon  disul- 
phide has  evaporated,  which  will  be  in  a  few  seconds,  ox- 
idation begins,  followed  very  quickly  by  the  ignition  of 
the  phosphorus.  An  instantaneous  or  nearly  instantane- 
ous combustion  is  called  an  explosion.  In  all  cases  the  to- 


OXYGEN    AND    OZONE 


57 


tal  amount  of  heat  produced  is  the  same :  in  slow  oxida- 
tions it  is  dissipated  as  fast  as  formed;  in  explosions,  the 
whole  generated  in  an  instant  of  time,  causes  enormous 
expansion  of  all  gases  produced  and,  as  a  result,  tre- 
mendous pressures  and  often  frightful  results. 

6.  Kindling  Temperature. — The  point  at  which  com- 
bustion begins  is  called  the  kindling  temperature.  For 
phosphorus  this  is  very  low ;  for  iron  very  high,  with  a 
great  variety  in  between  these  two.  A  bit  of  yellow 


Fig.    12. — Boiling  water  in  paper   cup. 

phosphorus  exposed  to  the  air  soon  reaches  its  kindling 
temperature ;  a  pile  of  shavings  needs  but  the  heat  of 
a  burning  match ;  while  anthracite  coal  must  be  fur- 
nished much  kindling  before  it  will  burn.  A  little  ex- 
periment giving  some  idea  of  the  kindling  point  of  pa- 
per, not  essentially  different  from  that  of  shavings,  may 
be  made  by  boiling  water  in  an  ordinary  sanitary  paper 
drinking  cup,  as  shown  in  Fig.  12.  In  a  few  minutes  the 


58  APPLIED    CHEMISTRY 

water  will  boil  vigorously,  but  as  the  temperature  of  the 
paper  is  not  greatly  above  that  of  the  boiling  water  it 
does  not  catch  fire. 

Ozone 

7.  What  Is  Ozone? — Ozone  is  an  unusual  form  of  ox- 
ygen, always  produced  when  an  electric  discharge  takes 
place  in  oxygen  or  in  the  air.    It  is  noticeable  about  the 
open  arc  in  stereopticon  work,  in  wireless  telegraphy, 
and  all  similar  places.     The  word   ozone   is  from  the 
Greek,  meaning  to  smell  and  was  given  this  gas  because  of 
its  peculiar  odor.    It  is  often  spoken  of  as  an  allotropic 
form  of  oxygen,  which  means  another  form.     Many  sub- 
stances appear  in  two  or  more  distinct  forms  almost  as 
different  from  each  other  as  if  they  were  not  related  at 
all;  usually  the  rarer  one,  or  more,  are  spoken  of  as  the 
allotropes  of  the  other,  or  the  allotropic  forms. 

8.  Preparation  of  Ozone. — To  secure  sufficient  ozone 
for  a  test,  a  stick  of  freshly  scraped  phosphorus  partly 
submerged  in  water  in  a  bottle  is  generally  used.     For 
the  test,  a  strip  of  white  paper  dipped  in  some  starch 
mucilage,  to  which  has  been  added  a  very  little  of  a 
solution  of  potassium  iodide,  is  suspended  in  the  bottle. 
In  a  short  time  the  paper  turns  blue.     The  ozone  has 
united  with  the  potassium,  has  set  the  iodine  free,  and 
this  has  formed  a  solution  with  the  starch  which  has  a 
blue  color.     It  is  believed  that  ozone  is  also  produced 
by  other  slow  oxidations.     It  is  probable,  that,  being  a 
form  of  oxygen,  ozone  is  always  produced  in  the  prep- 
aration of  oxygen  by  any  method.    However,  as  we  shall 
see  later,  ozone  is  a  very  unstable  body,  and  if  much 
heat  is  needed  or  produced  in  the  method  used  for  pre- 
paring oxygen,  most  of  the  ozone  will  be  decomposed  al- 


OXYGEN    AND    OZONE 


59 


most  immediately  into  ordinary  oxygen.  By  the  meth- 
ods already  suggested  for  the  preparation  of  oxygen,  by 
heating  mercuric  oxide  or  potassium  chlorate,  practi- 
cally 110  ozone  is  obtained.  But  if  a  method  is  used  in- 
volving the  application  of  no  heat  and  in  which  no  high 
temperature  is  reached  through  the  chemical  action,  ap- 
preciable amounts  of  ozone  ought  to  be  present.  Such 
a  method  may  be  tried  by  adding  a  few  drops  of  strong 
sulphuric  acid  to  a  solution  of  potassium  permanganate 


Fig.   13. — Machine  for   making  ozone. 

in  water.  The  bubbles  of  oxygen  may  be  seen  coming 
up  through  the  solution  and  the  odor  of  ozone  may  be 
readily  distinguished,  often  being  sufficiently  strong  to 
irritate  the  throat.  For  commercial  purposes  ozone  is 
now  prepared  by  means  of  apparatus  illustrated  in  Fig. 
13.  The  current  from  an  induction  coil  spreads  over  the 
tin  foil  coating  on  the  outside  of  the  outer  tube  through 
which  a  stream  of  oxygen  or  air  is  slowly  flowing,  as  indi- 


60  APPLIED    CHEMISTRY 

cated  by  the  two  arrows  at  E  and  D.  The  electricity  by 
brush  discharge  passes  across  to  the  tin  foil  coating  on  the 
inner  surface  of  the  other  tube  and  out  over  the  return 
wire.  Thus,  by  a  silent  discharge  of  the  current,  little  heat 
is  generated  and  a  very  appreciable  quantity  of  ozone  is 
present  in  the  escaping  current  of  air. 

9.  Characteristics. — Physical. — As  already  mentioned, 
ozone  has  a  peculiar  odor  and  is  irritating  to  the  throat 
and  bronchial  tubes,  if  present  in  considerable  quantities. 
It  is  blue  in  color.     It  is  much  more  soluble  in  water 
than  oxygen;  at  12°   C.   100  c.c.  of  water  will  dissolve 
about  50  of  ozone,  while  even  at  zero  only  4  c.c.  of  oxygen 
would  be  dissolved  by  the  same  volume  of  water.     Ozone 
is  also  very  soluble   in   turpentine   and  this  method   is 
sometimes  used  to  isolate  it  from  other  gases.     Having  a 
density   one   and  a  half  that   of   oxygen   indicates   that 
three  volumes  of  oxygen  have  been  condensed  to   form 
two  of  the  allotropic  form.    It  liquefies  at  -119°  C.     If 
a  current  of  ozone  mixed  with  air  be  passed  through  a 
tube  surrounded  by  liquid  oxygen,  the  ozone  is  readily 
liquefied,  while  most  "of  the  oxygen  will  escape  as  a  gas. 
Liquid  ozone  is  deep  blue  in  color  and  not  transparent  like 
liquid  oxygen. 

10.  Chemical    Characteristics. — The    most    important 
chemical  property  of  ozone  is  its  strong  oxidizing  power; 
it  is  also  very  unstable.    Mercury  and  silver  both  remain 
untarnished  in  pure  air,  but  in  ozone  they  are  quickly 
darkened.       It    attacks    many    other    substances    much 
more  actively  than  does  ordinary  oxygen. 

11.  Uses. — Ozonized  air,  prepared  as  described  in  a 
preceding  section,  is  now  used  in  many  photoplay  houses 
of  our  cities  as  a  means  of  vitalizing  or  purifying  the 
air.     Theoretically,  it  would  seem  to  be  an  excellent 
plan,  but  in  real  practice  there  seems  to  be  much  doubt 


OXYGEN   AND   OZONE  Cl 

on  the  part  of  some  as  to  its  efficiency.  In  some  large 
flour  mills,  the  wheat,  after  scrubbing,  is  passed  still 
damp  through  ozonizers  for  destroying  any  traces  of 
smut  or  mildew  not  removed  by  previous  processes  of 
milling.  In  some  cities  of  Europe,  ozone  is  used  as  is 
liquid  chlorine  in  this  country  for  purifying  the  water 
supplies.  It  is  claimed  that  a  gram  of  ozone,  which 
if  pure  would  be  only  about  a  half  liter,  or  one  pint,  is 
sufficient  to  destroy  as  many  as  30,000  bacteria  per 
cubic  centimeter  in  1,000  liters,  or  250  gallons.  As  there 
are  1,000  cubic  centimeters  in  a  liter,  this  would  mean 
that  a  half  liter  of  ozone  or  an  equivalent  mixed  with 
air  bubbled  slowly  through  250  gallons  of  water,  would 
be  sufficient  to  destroy  thirty  billion  bacteria. 

Exercises  for  Review 

1.  What  part  of  the  earth's  crust  does  oxygen  form?     Give  its 
proportions  in  several  familiar  things. 

2.  What  two  men  first  prepared  oxygen?     What   did  they  use? 

3.  What  is  the  usual  method  in  the  laboratory?     Define  cataly- 
sis.    Name  some  other  instance  of  catalytic  action. 

4.  Give  its  chief  physical  and  chemical  characteristics.     How  did 
it;  receive  the  name  oxygen?     What  other  names  was  it  known  by  in 
an  early  day? 

5.  Name  the  most   important  uses   of  oxygen.     Give  five  minor 
uses. 

6.  Define    oxidation,    combustion,    explosion.      How   can   you   ac- 
count for  spontaneous  combustion?     Give  some  case  where  caution 
must  be  exercised  about  the  home. 

7.  What  is  meant  by  the  kindling  temperature  of  a  substance? 
Name  one  substance  with  very  lowr  kindling  point:    one  with  very 
high. 

8.  Has   water   a   kindling   temperature?      Give    reason   for   your 
answer. 

9.  What  is  ozone?     Origin  of  its  name?     What  is  an  allotrope? 


G2 


APPLIED    CHEMISTRY 


10.  Give  two  ways  of  preparing  ozone  and  method  of  testing  its 
presence. 

11.  How  is  ozone  prepared  on  a  large  scale? 

12.  Compare  ozone  with  oxygen. 

13.  Give  three  uses  of  ozone. 

14.  "When  a  bellows  is  used  to  cause  a  fire  to  burn  faster,  is  the 
action  catalytic?    Explain. 


CHAPTER  IV 

HYDROGEN 
Outline — 

History  of  Hydrogen 

Occurrence 

Preparation 

(«)    From  Water 

(b)  From  Acids 

(c)  From  Oils 
Characteristics  of  Hydrogen 

(«)   Physical 

(Z>)   Chemical 
Practical  Uses 
The  Phlogiston   Theory  of  Combustion 

1.  History. — It  is  presumed  that  Paracelsus,  the  great 
physician-chemist  in  the  sixteenth   century,   discovered 
hydrogen,  for  he  carried  out  experiments  that  involved 
the  preparation  of  it.     But  he  records  no  facts  regard- 
ing it  and  may  have  overlooked  it  entirely.     In  1766, 
Cavendish,  an  English  chemist,  prepared  hj'drogen  and 
recognized  it  as  a  new  substance  but  did  not  consider 
it  an  element.    He  called  it  inflammable  air.    Later  when 
it  was  discovered  that  in  burning,  it  produces  water,  it  was 
given  its  present  name  which  is  from  the  Greek,  meaning 
waicr  producer. 

2.  Occurrence. — It    lias    been    stated    that  hydrogen 
ranks  ninth  in  abundance  among  the  elements.    In  many 
ways,  however,  it  is  an  important  element.     It  consti- 
tutes  as   previously   seen,    one-ninth    of   the   weight    of 
water;  it  is  an  important  constituent  of  nearly  all  or- 
ganic matter  such  as  oils  and  fats,  sugars,  starches  and 
the  like;  also  of  all  acids,  many  of  which  are  already 

63 


64  APPLIED   CHEMISTRY 

familiar  to  the  student.  For  example,  acetic  acid  in 
vinegar,  citric  in  lemons  and  grape  fruit,  oxalic  in  rhu- 
barb as  well  as  several  others,  are  well  known.  In  the 
laboratory  the  most  common  acids  are  hydrochloric,  sul- 
phuric and  nitric. 

3.  Preparation  from  Water.— The  preparation  of  hy- 
drogen by  the  electrolysis  of  water  has  already  been 
described.  With  the  ordinary  laboratory  apparatus  it 
is  a  slow  process,  but  the  gas  obtained  is  very  pure  and 
sometimes  this  fact  overbalances  the  lack  of  rapidity. 
Hydrogen  may  also  be  prepared  from  water  by  treating 
with  some  metal,  as  sodium  or  potassium.  It  may  seem 
strange  that  a  metal  could  do  this.  It  has  been  seen  al- 
ready that  hydrogen  belongs  among  the  electropositive 
elements.  It  must  be  stated,  however,  that  some  ele- 
ments are  much  more  positive  in  their  behavior  than 
others.  Without  attempting  to  be  very  exact,  the  ele- 
ments may  be  arranged  and  compared  to  the  parts  of 
a  bar  magnet,  as  illustrated  in  Fig.  14.  If  the  magnet  is 
laid  down  upon  a  sheet  of  paper  upon  which  iron  filings 
have  been  sprinkled,  most  of  the  filings  will  be  at- 
tracted to  the  ends  which  are  called  the  poles  of 
the  magnet,  with  the  quantity  rapidly  diminishing 
toward  the  center.  In  a  similar  way  the  elements  may 
be  arranged  in  the  order  of  their  electropositive  charac- 
ter, and  those  the  better  known  to  the  student  are  thus 
shown  in  Fig.  14.  It  will  thus  be  seen  that  hydrogen  is 
well  down  the  list.  Naturally,  therefore,  such  elements  as 
pcttassium  and  sodium  would  be  presumed  to  have  the 
power  of  taking  a  negative  element  away  from  hydrogen 
and  setting  it  free.  Experiment  shows  that  potassium  does 
this  violently,  such  that  even  on  cold  water  the  hydro- 
gen set  free  is  ignited  almost  instantly  and  unless  the 
piece  of  potassium  is  very  small  even  it  will  burst  into 


HYDROGEN  G5 

pieces  from  the  heat  generated.  Sodium,  though  much 
less  active,  decomposes  water  rapidly,  but  unless  the 
water  is  warm  the  hydrogen  is  not  ignited.  With  mag- 
nesium the  water  must  be  hot  for  even  moderate  re- 
sults. In  using  sodium,  since  the  metal  melts  almost 


K 
Na 
Ca 
M£ 
Al 
Zn 
Fe 
Sn 
Pb 
H 
Cu 


Au 


Fig.    14. — Electromotive    series    ot    metals    and    bar    magnet    with    iron    filings 

attached. 

instantly  when  it  touches  the  water,  because  of  the 
heat  generated  by  the  chemical  action,  a  gauze  spoon 
is  employed  as  shown  in  Fig.  15.  The  sodium  is  enclosed 
in  this,  inserted  under  the  mouth  of  the  test  tube  or 
bottle,  which  is  filled  with  water  and  inverted  over  a 


66  APPLIED    CHEMISTRY 

trough  of  water,  whereupon  the  gas  rises  and  fills  the 
bottle.  It  is  a  method  somewhat  expensive,  but  the  gas 
obtained  is  pure. 

4.  Obtaining  Hydrogen  from  Acids. — As  hydrogen 
may  be  expelled  from  water  so  it  may  be  from  acids, 
in  a  similar  way  and  for  the  same  reason.  A  very  con- 
siderable number  of  metals  might  be  used.  Sodium 
and  potassium  would  do,  but  their  action  is  dangerously 
violent;  hence,  it  should  not  be  attempted.  It  is  custo- 
mary to  use  some  metal  much  farther  down  the  electro- 
motive series,  whereby  the  action  is  much  slower.  In 
the  laboratory  zinc  is  most  often  used  either  with  hy- 


Fig.    15. — Preparing   hydrogen   from   water    by    means   of   sodium. 

drochloric  or  sulphuric  acid  diluted.  Iron  is  cheaper 
and  is  used  when  large  amounts  are  desired,  but  the 
gas  is  not  so  pure  as  when  zinc  is  employed.  The  metal 
in  mossy  form,  is  put  into  the  generating  flask  and 
barely  covered  with  water.  When  the  receiving  bottles 
are  ready  in  the  trough,  the  acid  is  added  through  the 
thistle  tube  a  little  at  a  time  until  action  begins.  The 
thistle  tube  must  dip  below  the  surface  of  the  water 
in  the  flask  (Fig.  16). 

5.  Preparation  of  Hydrogen  from  Oils. — It  is  possible 
by  heat  alone  to  obtain  hydrogen  from  such  oils  as  kero- 
sene and  similar  oils,  prepared  from  crude  petroleum 


HYDROGEN 


67 


by  distillation.  But  the  gas  thus  obtained  is  only  about 
50  per  cent  hydrogen,  the  remainder  being  a  variety. 
Yet  for  some  purposes  even  this  is  sufficiently  pure  and 
is  exceedingly  cheap. 

6.  Characteristics  of  Hydrogen,  Physical. — Hydrogen 
'is  an  odorless,  colorless  gas,  the  lightest  known.  It 
is  only  about  one-fourteenth  as  heavy  as  air,  so  that 
something  over  11  liters  are  necessary  to  weigh  1  gram. 
It  is  a  fairly  good  conductor  of  heat,  which  cannot  be 
said  of  any  other  gas.  It  may  be  liquefied  at  a  tem- 
perature of  about  -252°  C.  in  which  condition  it  is  color- 
less. At  -256°  C.  it  becomes  a  solid.  One  of  the  most 


Fig.    16. — Preparation    of    hydrogen   from    acids. 

interesting  of  its  physical  properties  is  its  ability  of 
be  ing  absorbed  by  certain  metals  with  the  evolution 
of  heat.  This  may  be  shown  by  the  platinum  sponge  held 
over  a  jet  of  escaping  hydrogen.  In  a  very  few  seconds 
the  sponge  becomes  red-hot  and  the  hydrogen  is  ig- 
nited. It  may  likewise  be  shown  by  lowering  the 
sponge  into  a  bottle  of  hydrogen  and  oxygen  mixed  in 
about  the  proportions  of  2  to  1.  The  sponge  quickly 
becomes  red  and  the  gases  explode  violently.  There 
is  no  danger,  however,  if  a  wide  mouthed  bottle  is  used. 
This  property  is  often  called  occlusion.  Palladium  has 


68  APPLIED    CHEMISTRY 

more  remarkable  powers  for  absorbing  hydrogen  than 
has  platinum,  in  that  it  will  take  up  nearly  seven  hun- 
dred times  its  own  volume  of  the  gas.  Hydrogen  read- 
ily passes  through  unglazed  porcelain  and  cracks  in  bot- 
tles which  would  not  leak  water,  and  a  cork  made  of  plas- 
ter of  paris  is  so  porous  as  to  offer  little  obstruction  to  the 
escape  of  the  gas.  For  the  same  reason,  toy  balloons 
soon  lose  their  buoyancy. 

7.  Chemical  Characteristics. — Hydrogen  burns  with  a 
very  pale  blue  flame  with  intense  heat.  If  the  delivery 
tube  be  glass,  it  is  soon  heated  to  redness,  when  the 
flame  becomes  visible,  because  of  the  constituents  of 
the  glass  giving  a  yellow  color.  One  gram  of  hydrogen 
in  burning  will  produce  more  than  four  times  as  many 


Fig.    17. — Oxyhydrogen  blowpipe. 

heat  units  as  the  same  weight  of  anthracite  coal.   Water 
is  the  sole  product  of  combustion. 

8.  Practical  Uses. — One  valuable  use  is  in  the  oxyfe^j- 
drogen  blowpipe  or  torch  as  it  is  often  called.  It  is  il- 
lustrated in  Fig.  17.  The  hydrogen  enters  through  one 
pipe  and  the  oxygen  by  the  other,  and  near  the  point 
where  ignited  they  are  thoroughly  mixed.  The  stop- 
cocks are  so  opened  by  the  operator  as  to  furnish  twice 
as  much  hydrogen  as  oxygen.  Intense  heat  is  thus  ob- 
tained, ranging  in  temperature  from  2,000°  to  2,500°  C., 
at  which  platinum  and  other  refractory  metals  are  read- 
ily melted.  If  this  flame  be  allowed  to  impinge  upon  a 
stick  of  lime,  it  gives  a  dazzling  white  light,  called  the 
calcium  ,or  Drummond  light.  Up  to  the  introduction  of 


HYDROGEN  G9 

the  electric  arc,  this  was  the  best  and  commonly  used  light 
for  stereopticons  and  stage  effects.  Another  use  for  hy- 
drogen is  in  filling'  balloons.  Especially  during*  the  world 
war  was  this  extensive  for  dirigibles  and  for  observation 
balloons.  For  some  purposes  natural  gas  may  be  used 
and  has  often  been  in  flight  contests,  but  it  is  eight  times  as 
heavy  as  hydrogen,  hence  does  not  compare  in  efficiency. 
However,  its  loss  through  diffusion  would  be  much  slower. 
For  short  flights,  such  as  those  seen  at  amusement  parks 
and  the  like,  the  balloons  are  usually  filled  by  heating 
kerosene  or  naphtha,  as  suggested  in  a  preceding  section. 
As  this  is  often  done  by  spraying  the  oil  upon  a  bed  of  hot 
coals,  there  is  usually  some  small  amount  of  air  present 
and  some  imperfect  combustion  resulting  in  the  forma- 
tion of  some  smoke.  For  this  reason,  when  the  aeronaut 
leaps  from  the  car  in  the  parachute,  a  puff  of  smoke  is 
often  seen  emerging  from  the  capsized  balloon. 

9.  An  Old  Theory  of  Combustion.— Combustion  is  now 
well  understood,  but  during  the  last  quarter  of  the 
eighteenth  century  it  was  a  matter  of  constant  study 
and  of  much  dispute.  With  the  exception  of  Lavoisier, 
who  lost  his  life  at  the  time  of  the  French  Revolution, 
practically  all  the  chemists  of  that  day  accepted  the 
theory  that  a  substance  called  phlogiston  was  contained 
in  every  combustible  substance,  and  that  it  escaped  as 
the  substance  was  burned.  The  great  French  chemist 
never  accepted  this  theory ;  and  finally  by  the  use  of  the 
balance,  which  up  to  that  time  chemists  had  not  employed 
to  any  great  extent,  he  succeeded  in  showing  the  fallacy 
of  the  phlogistic  theory.  It  is  now  known  that  when  a 
metal  or  any  substance  is  burned,  if  all  the  products  of 
combustion  are  saved  and  weighed,  the  total  is  greater 
than  the  weight  of  the  original  substance.  Lavoisier 
called  attention  to  this  fact,  and  argued  that  if  something 


70 


APPLIED    CHEMISTRY 


escaped,  the  resulting  oxides,  or  calces,  as  they  were 
called  in  that  day,  ought  to  weigh  less.  The  upholders 
of  the  theory  replied  that,  since  phlogiston  is  an  exceed- 
ingly light  substance,  it  has  a  buoyant  effect  upon  what- 
ever contains  it,  and  therefore,  the  more  there  is  the 


Fig.    18.— Lavoisier,   beheaded   in   French    Revolution,   was    the    Father    of 
Modern   Chemistry. 

lighter  the  object.  When  hydrogen  was  discovered  and 
its  extreme  lightness  noted,  as  well  as  its  great  combusti- 
bility, many  of  the  phlogistonists  believed  they  had  dis- 
covered phlogiston  and  regarded  it  as  upholding  their 


HYDROGEN  71 

theory.  But,  in  the  light  of  what  the  balance  continu- 
ally showed,  they  were  finally  obliged  to  acknowledge  the 
fallacy  of  their  position  and  that  Lavoisier  was  correct. 

Exercises  for  Review 

1.  Give  a  brief  account  of  the  discovery  of  hydrogen.     How  did 
it  come  to  receive  its  present  name? 

2.  Name    some    very    common    substances    containing    hydrogen. 
How  does  it  rank  among  the  elements  in  total  amount? 

3.  Give  two  ways  of  obtaining  hydrogen  from  water.     What  can 
be  said  about  the  value  of  these  methods? 

4.  What  do  you  understand  by  the  electromotive  series  of  met- 
als?    Where  does  hydrogen  come  in  this  series? 

5.  How  may  hydrogen  be   obtained   from   acids?     What  metals 
are  best?    Why?    What  acids  are  generally  used?    Would  nitric  do? 

6.  How  may  hydrogen   be   obtained  from   kerosene  or  gasoline? 
What  is  true  of  the  purity  of  the  gas  thus  obtained? 

7.  Give  the  chief  characteristics  of  hydrogen.     Explain  what  is 
meant  by  occlusion.     Give  two  experiments  to  illustrate. 

8.  Give  three  important  uses  of  hydrogen.     What  is  the  Drum- 
mond  light? 

9.  Give  briefly  the  phlogiston  theory  of  combustion.     What  was 
the  most  absurd  thing  about  this  theory?    Who  finally  overthrew  it? 


CHAPTER  V 

THE  ATMOSPHERE 
Outline — 

Early  ideas  of  the  Air 
Composition  of  Air 

Proportions 

Proof  that  Air  is  Mixture 
Diffusion  of  Gases 
Ventilation 
Purposes  of  the  Constituents 

(a)    The  Oxygen 

(&)   Nitrogen 

(c)   Carbon  Dioxide 

(d~)   Water  A7apor 
Humidity  and  Health 
Liquid  Air 
Argon  and  Helium 

1.  Early  Ideas  of  the  Air. — Even  before  the  begin- 
ning of  the  Christian  era  the  air  was  an  object  of  in- 
terest among  philosophers.  For  centuries  thereafter, 
however,  little  advancement  was  made  in  the  knowledge 
concerning  it,  for  the  reason  that  no  experimental  study 
of  it  was  attempted.  In  the  latter  part  of  the  eighteenth 
century  when  the  phlogiston  theory  was  at  its  height 
a  very  considerable  number  of  gases  was  discovered  and 
the  air  itself  received  a  very  careful  study  in  its  rela- 
tion to  combustion.  Even  thus,  until  near  the  end  of 
the  century,  all  the  gases  known  were  regarded  as 
modifications  of  atmospheric  air  and  were  named  ac- 
cordingly. Thus,  Cavendish  called  hydrogen  inflamma- 
ble air;  Scheele  called  oxygen  fire  air;  Priestley  named 
it  depklogisticated  air;  Black,  the  discoverer  of  carbon 
dioxide  called  it  fixed  air;  nitrogen  was  known  as  azote 

72 


THE    ATMOSPHERE  To 

or  phlogisticated  air  and  so  on.  As  we  have  seen  it  was 
Lavoisier  who  overturned  the  prevalent  ideas  and  sug- 
gested suitable  names  for  some  of  the  gases  of  recent  dis- 
covery. 

2.  Components  of  the  Air. — In  what  is  often  spoken  of 
as  pure  air  there  are  always  found  nitrogen,   oxygen, 
argon,  carbon  dioxide  and  water  vapor,  besides  minute 
quantities  of  a  few  very  rare  elements.     Sometimes  the 
first   three    of   these    are    regarded   as    the    atmosphere 
proper,  for  the  reason  that  the}"  vary  little;  but  when 
the  evident  purposes  of  the  air  are  considered,  the  other 
two  are  essentials,  and  in  the  following  study  will  be 
regarded  as  constituents.    For  years  the  air  was  believed 
to  contain  the   two  main  gases  in  the  form  of  a  com- 
pound.    At  that  time,  the  presence   of  argon  was  not 
known  and  the  apparent  unvarying  proportion  of  oxygen 
and  nitrogen  led  chemists  to  believe  they  were  in  com- 
bination. 

3.  Proportions  of  These  Constituents. — By  volume  the 
oxygen  in  the  air  constitutes  about  21  per  cent;  the  ni- 
trogen, 78  per  cent ;  the  argon,  a  little  less  than  1  per 
cent — 0.94 — and  the  carbon  dioxide,  about  .03  per  cent, 
with  the  water  vapor  decidedly  variable.    If  the  air  were 
of  the  same  density  throughout,  it  would  extend  above 
the  surface  about  five  miles.     Then  if  the  various  con- 
stituents were  arranged  in  layers  about   the   earth,  in 
accordance  with  their  respective  densities,  there  would 
be  nearest  the  ground  a  layer  of  water  about  5  inches 
d?ep;  above  that,  one  of  argon,  about  250  feet  deep; 
then  carbon  dioxide,  12  or  13  feet;  above  that,  oxygen 
one  mile,  and  lastly  the  nitrogen,  four  miles. 

4.  Proof  That  Air  Is  a  Mixture. — There  is  very  strong 
and   convincing   evidence   now   that   air   is   a   mixture. 
When  pure   distilled   water   is   exposed   to   the   air,   al- 


74  APPLIED    CHEMISTRY 

though  the  amount  of  nitrogen  is  about  four  times  that 
of  the  oxygen,  the  oxygen  absorbed  is  nearly  double 
that  of  the  nitrogen.  If  the  air  were  a  compound,  the 
absorption  of  the  two  gases  would  necessarily  be  in  the 
proportion  in  which  they  entered  into  the  compound. 
Again,  air  is  now  readily  liquefied.  When  this  hap- 
pens the  carbon  dioxide  and  the  water  vapor  solidify 
and  precipitate  out.  A  vessel  of  liquid  air  left  standing 
shows,  when  about  four-fifths  of  it  has  boiled  away, 
that  the  residue  is  nearly  pure  oxygen.  This  would  be 
possible  only  if.  the  air  were  a  mixture  and  the  boiling 
point  of  nitrogen  lower  than  that  of  oxygen.  Alcohol 
in  boiling  gives  off  vapor  of  the  same  composition  as 
the  liquid  and  so  does  every  liquid  compound.  Air, 
therefore,  cannot  be  a  compound.  Again,  every  com- 
pound consists  of  two  or  more  elements  in  unvarying 
proportions.  In  the  air  the  oxygen  may  vary  as  much 
as  three-fourths  of  1  per  cent.  Not  only  these,  but  other 
proofs  make  it  sure  that  the  air  is  a  mixture  and  not 
a  compound. 

By  weight  the  constituents  are— 

Nitrogen 75.46  per  cent 

Oxygen    23.18  " 

Argon    1.29          ' ' 

Carbon  Dioxide    03  to     .04          " 

Water    Vapor    Variable 

Other  rare  Gases.  .  .Very  small  amounts 

5.  Diffusion  of  Gases, — If  in  a  tall  cylinder  nearly 
filled  with  water,  colored  blue  with  litmus,  a  few  cu- 
bic centimeters  of  sulphuric  acid  be  introduced  be- 
low the  water  by  means  of  a  pipette,  in  two  or  three 
days  the  heavy  acid  will  have  moved  upward  through 
the  entire  mass  of  water.  This  will  be  known  by  the 
litmus  solution  turning  red,  as  it  does  in  the  pres- 


THE    ATMOSPHERE  75 

ence  of  any  acid.  Likewise  any  gas  tends  to  occupy 
all  the  space  afforded  it.  If  a  cylinder  of  ammo- 
nia be  inverted  over  one  of  hydrogen  chloride,  al- 
though the  lighter  gas  is  above  one  more  than  twice 
as  heavy,  in  a  very  few  minutes  the  two  will  be  evenly 
distributed  throughout  the  entire  space,  as  can  be  seen 
by  the  action  which  takes  place.  This  shows  that  the 
particles  of  a  gaseous  body  are  apparently  moving  in 
all  directions  all  the  time  regardless  of  their  density. 
This  explains  largely  why  the  air  is  always  a  practically 
uniform  mixture.  Equilibrium  is  constantly  being  de- 
stroyed by  various  processes  of  nature  and  otherwise, 
but  diffusion,  as  this  movement  is  called,  aided  by  wind 
currents,  keeps  the  composition  practically  constant. 

6.  Value  of  Each  Constituent. — It  has  been  stated  in 
a  preceding  chapter  that  oxygen  is  necessary  for  respi- 
ration. When  taken  into  the  lungs  it  enters  into  a  loose 
combination  with  the  hemoglobin  and  is  by  the  circu- 
lation taken  throughout  the  body.  Meeting  the  carbon 
in  the  various  tissues,  carbon  dioxide  is  formed  and  by 
the  oxidation  heat  is  produced.  Thus  the  body  is  warmed. 
In  aquatic  animals  where  the  only  oxygen  attainable 
is  the  small  amount  dissolved  in  the  water,  the  quantity 
of  carbon  consumed  in  the  tissues  is  small,  and  thus 
little  heat  is  produced.  Such  animals  are  "cold 
blooded";  naturally,  therefore,  the  food  required  to 
sustain  life  is  small  in  proportion.  A  good  comparison 
may  be  had  by  noting  the  amount  of  food  consumed 
by  a  canary  bird  and  a  gold  fish  of  about  the  same 
weight.  The  human  body  of  average  size  consumes 
daily  about  750  grams  or  26  ounces  of  oxygen.  This 
is  the  equivalent  of  the  entire  amount  of  oxygen  con- 
tained in  over  2,600  liters  of  air.  From  this  is  produced 
carbon  dioxide  to  the  amount  of  about  2.2  pounds  or 


76  APPLIED    CHEMISTRY 

1,000  grams.  When  the  air  leaves  the  lungs  at  each 
respiration  only  about  16  per  cent  of  oxygen  remains 
instead  of  the  original  23  per  cent,  while  the  carbon 
dioxide  in  the  exhaled  breath  is  present  to  the  extent 
of  about  4.4  per  cent  or  more  than  100  times  as  much 
as  is  contained  in  ordinary  air. 

7.  Ventilation. — It  is  apparent  from  the  above  how  im- 
portant good  ventilation  becomes.     This  importance  is 
emphasized  when  it  is  remembered  that  while  the  first 
respiration  of  a  given  volume  of  air  removes  over  one- 
fourth  of  the  oxygen,  the  second  inhalation  of  the  same 
volume  of  air  only  takes  about  the  same  proportion  of 
what  remains.    Thus  the  body  in  obtaining  impoverished 
air  is  not  receiving  anything  like  the  amount  needed. 
Lack  of  proper  ventilation  is  most  apt  to  be  found  in 
school  rooms  or  other  places  where  people  congregate 
in  considerable  numbers,  as  photoplay  houses,  theaters, 
and  the  like.    Health  boards  in  many  cities  require  that 
means  shall  be  provided  for  furnishing  30  cubic  feet  of 
fresh  air  per  minute  per  individual.     In  the   ordinary 
home  where  the  family  is  small  there  is  no  special  pro- 
vision needed,  for  even  in  cold  weather  when  doors  and 
windows  are  closed  there  is  sufficient  leakage  to  fur- 
nish  an  abundance   of  fresh   air.     It   is   only   in   poor 
tenement  houses  and  basements  used  as  homes,  where 
large  families  are  often  found,  that  the  lack  of  ventila- 
tion is  apparent  in  the  home. 

8.  Value  of  the  Nitrogen. — To  the  human  body,  nitro- 
gen, as  it  exists  in  the  air  in  a  free  state,  seems  to  serve 
no  other  purpose  than  to  dilute  the  oxygen.    A  fish  out 
of  water  dies,  partly  probably  because  of  the  very  rich, 
atmosphere  it  is  compelled  to  breathe.    In  the  same  way 
the  human  body,  as  at  present  constituted,  could  prob- 
ably not  inhale  pure  oxygen  continuously  without  un- 


THE    ATMOSPHERE 


77 


due  stimulation  and  serious  results.  In  the  combined 
form  nitrogen  enters  into  the  muscular  part  of  the  body 
and  only  through  the  use  of  nitrogenous  foods  can  its 
waste  be  repaired.  Neither  animals  nor  plants,  as  a 
general  rule,  can  obtain  nitrogen  directly  from  the  air, 
at  least  in  sufficient  quantities  to  meet  their  necessities. 
Animals  secure  it  mainly  through  lean  meats  or  legu- 
minous foods  such  as  beans,  peas  and  the  clovers.  Most 
plants  in  continuously  cultivated  fields  obtain  their 


Fig.    19. — Nodules   in   which    the   nitrogen-fixing    bacteria   live    on    the   roots   of 
a  bean.      (From   Warren — Klements   of  Agriculture.) 

needed  supply  through  fertilizers,  which  are  largely  ob- 
tained from  the  waste  eliminated  by  the  animal  economy. 
So  it  will  be  seen  there  is  an  endless  cycle  existing  here 
in  which  animals  and  plants  each  supplement  the  needs 
of  the  other.  It  should  be  stated,  however,  that  there 
is  one  class  of  plants  which,  fortunately,  is  able  through 
the  aid  of  bacteria  to  obtain  the  nitrogen  needed  di- 
rectly from  the  air.  These  are  the  legumes,  and  agricul- 


78  APPLIED    CHEMISTRY 

turists  at  present  are  employing  this  means  extensively 
in  restoring  the  needed  nitrogen  to  the  soils.  The  accom- 
panying figure  shows  the  nodules  upon  the  roots  of  a 
bean  plant,  formed  by  the  nitrogen  fixing  bacteria. 
(Fig.  19.) 

9.  Carbon  Dioxide. — It  will  be  learned  later  that  car- 
bon dioxide  is  an  inert  gas  as  far  as  the  human  system 
is  concerned,  in  that  it  is  devoid  of  toxic  effects.  It  is 
true,  however,  that  a  considerable  quantity  of  it  in  the 
air  usually  indicates  the  presence  of  other  substances 
deleterious  to  health.  This  is  especially  true  if  the  air 
be  impoverished  by  frequent  respiration  and  therefore 
abounding  in  the  waste  materials  thrown  off  from  the 
body.  It  is  this  condition  mainly  that  proper  ventilation 
seeks  to  avoid.  Health  experiments  carried  out  in  such 
places  as  breweries,  where  considerable  amounts  of  car- 
bon dioxide  are  continually  escaping  into  the  air,  shoAV 
that,  other  conditions  not  being  unfavorable,  headache 
and  drowsiness,  usually  apparent  in  poorly  ventilated 
rooms,  do  not  occur  and  no  unfavorable  results  follow. 
To  plants,  carbon  dioxide  is  as  essential  as  oxygen  to 
animals.  The  leaves,  corresponding  to  the  lungs  of  the 
body,  absorb  the  carbon  dioxide  and  under  the  influence 
of  sunlight  are  able  to  decompose  it.  In  the  plant  labor- 
atory the  carbon  is  combined  with  the  water  obtained 
from  the  soil  and  cellulose  results  to  build  the  woody 
structure  of  the  plant  or  tree.  Another  arrangement 
by  another  plant  produces  starch  or  sugar  and  a  great 
variety  of  other  well-known  substances.  But  they  all 
come  primarily  from  the  carbon  dioxide  obtained  from 
the  air  through  the  leaves  and  must  have  the  heat  and 
light  of  the  sun  for  the  process.  It  is  seen,  therefore, 
as  in  the  case  of  the  nitrogen,  that  there  is  an  endless 
cycle  in  the  transference  of  carbon  from  the  animal  to 


THE    ATMOSPHERE  79 

the  vegetable  world  and  back  again,  and  that  the  ex- 
istence of  either  without  the  other  would  in  all  proba- 
bilit3r  not  be  of  long  endurance. 

10.  The  Water  Vapor.— It  has  been  stated  that  the 
water  vapor  in  the  air  varies  greatly.    The  amount  that 
can   be  held  is  dependent  upon   the   temperature.     At 
0°  C.  a  cubic  meter,  which  is  something  more  than  a  cubic 
yard,  is  able  to  hold  only  4.87  grams  of  water:  at  10° 
C.   it  can  hold  9.92  grams;   at  20°,  which  is  but  little 
cooler  than   ordinary  room   temperature,   17.16   grams. 
For   health,    from    two-thirds    to    three-fourths    of    the 
amount   specified  at  room  temperature   is  regarded   as 
best;  more  than  this,  if  the  temperature  be  high,  is  op- 
pressive.    The  reason  is  that  the  human  body  regulates 
its  temperature   by  the   evaporation  of  Avater  through 
the  pores  of  the  skin.     A  single  gram  of  water  for  its 
evaporation  requires  something  like  550  calories  of  heat; 
an  ounce  of  water,  which  is  about  28  grams,  in  being 
evaporated  from  the  surface  of  the  human  body,  would 
reduce  the  temperature  of  the  entire  body  of  150  pounds 
weight  about  .5  of  a  degree.    Anything  therefore,  which 
prevents   or   retards   evaporation   prevents   the   cooling 
of  the  body.     When  the  humidity  is  high,  as  it  often 
is  in  summer  in  the  Atlantic,  Gulf  and  Mississippi  Valley 
states,  the  air  surrounding  the  body  is  already  nearly 
saturated  Avith  moisture.  This  greatly  retards  evapora- 
tion,  and   interferes   with   the   regulation   of   the   body 
temperature. 

11.  Moisture  and  Health. — The  public  has  been  more 
or  less  well  informed  as  to  the  importance  of  fresh  air; 
but  the  humidity  of  the  air  in  the  home  in  winter  has 
not  been  greatly  considered.     As  stated  already,  air  at 
0°  C.  or  32°  F.  can  hold  only  4.87  grams  of  water  vapor. 
Usually  there  is  present  not  one-half  this  amount.     This 


80  APPLIED   CHEMISTRY 

air  is  taken  into  our  homes,  warmed  to  20°  or  21°  C.  or 
about  70°  F.,  without  the  addition  of  any  appreciable 
amount  of  water.  The  result  is  a  condition  decidedly 
adverse  to  health.  Unduly  dry  nasal  passages,  irritated 
throat  and  bronchi,  susceptibility  to  colds,  chapped 
hands  and  skin  and  other  evils  follow.  The  question  of 
humidity  is  now  carefully  considered  by  architects  in 
the  construction  of  large  school  buildings  and  the  mois- 
ture content  of  the  air  is  kept  reasonably  uniform  by 
artificial  means.  In  the  homes  like  provision  should  be 
made.  As  it  is  not  provided  by  the  usual  methods  of 
construction  and  heating,  the  individual  must  do  this 
himself.  In  rooms  heated  by  radiators,  either  steam  or 
hot  water,  a  towel  suspended  from  a  rack,  fastened 
behind  the  radiator  and  dipping  in  a  pan  of  water  sit- 
ting on  the  floor,  will  be  out  of  sight  and  will  furnish 
ample  moisture.  With  hot  air  furnaces  the  problem  is 
more  difficult.  It  may  be  partially  met  by  putting  shal- 
low pans  of  water  beneath  each  register  where  such  are 
located  in  the  floor.  When  not,  each  case  with  its  pos- 
sibilities must  be  taken  up  by  itself.  It  is  a  problem 
the  student  should  interest  himself  in  for  the  benefit 
of  everyone  in  the  home. 

12.  Liquid  Air.— For  some  years  air  has  been  lique- 
fied in  commercial  quantities.  The  principle  underly- 
ing is  that  ordinary  gases  expanding  from  great  pres- 
sure into  a  more  or  less  perfect  vacuum  are  cooled.  In 
the  apparatus  used,  this  cooled,  expanded  air  is  com- 
pelled to  pass  out  around  the  pipe  through  which  the 
compressed  air  is  entering.  Thus  at  each  impulse  of 
the  pump,  cooler  and  cooler  portions  of  air  are  forced 
out  around  the  incoming  supply,  until  eventually  the 
point  of  liquefaction  is  reached.  It  is  a  colorless  liquid, 
like  water,  and  usually  consists  of  50  per  cent  or  more 


THE   ATMOSPHERE  81 

of  oxygen  instead  of  23  per  cent  as  in  the  atmosphere. 
The  reason  is  that  the  boiling  point  of  nitrogen  is  194° 
C.  below  zero,  while  that  of  oxygen  is  ll1/^  degrees 
higher.  Thus  from  the  constant  loss  of  the  nitrogen 
through  evaporation  the  proportion  of  oxygen  continu- 
ally increases  the  longer  the  vessel  stands.  Liquid  air  is 
kept  and  shipped  in  what  are  called  Dewar  bulbs,  shown 
in  Fig.  20.  They  are  the  original  of  what  the  public 
knows  as  thermos  bottles,  being  double-walled  flasks  with 
a  vacuum  between  and  the  walls  coated  with  silver. 

13.  Argon  and  Helium. — It  has  long  been  known  that 
nitrogen  prepared  from  the  air  is  heavier  than  samples 
made  from  various  nitrogen  compounds.  This  led  to 


Fig.   20. — Dewar  bulbs.     The  thermos  bottle   is  merely  different  in   shape. 

the  suspicion  that  there  was  some  heavier  gas  mixed  with 
it.  Even  as  early  as  the  latter  part  of  the  eighteenth 
century,  Cavendish,  the  discoverer  of  hydrogen,  was 
convinced  that  atmospheric  nitrogen  contained  another 
gas  and  attempted  to  prove  it  experimentally.  In  elim- 
inating the  nitrogen  he  had  as  a  residual  gas  only  a 
small  bubble  which  he  concluded  to  disregard.  He  prob- 
ably used  too  small  quantities  of  air,  for  Ramsey,  in 
3894,  by  practically  the  same  experiment  succeeded  in 
obtaining  sufficient  quantity  of  the  argon  to  prove  it 
was  the  same  gas  he  had  obtained  by  another  method 
of  separating  it  from  nitrogen.  It  is  an  inert  gas  and 


82  APPLIED    CHEMISTRY 

received  the  name  "argon"  from  a  Greek  word,  meaning 
lazy  or  inactive.    No  compounds  of  argon  are  known. 

14.  Helium. — The  word  is  derived  from  the  Greek  for 
sun,  and  the  name  was  given  to  this  element  because  be- 
fore it  was  known  upon  the  earth  a  line  in  the  orange 
band  of  the  solar  spectrum  was  observed  which  belonged 
to  some  undiscovered  element.  Later,  it  was  discovered 
in  certain  spring  waters ;  it  may  be  -obtained  from  cer- 
tain minerals,  compounds  of  uranium  and  thorium  and 
is  found  in  minute  quantities  in  the  air.  It  is  a  gas  which 
is  harder  to  liquefy  than  is  hydrogen,  having  a  boiling 
point  of  -268.5°  C.  It  is  only  twice  as  heavy  as  hydro- 
gen and  unlike  hydrogen  is  not  combustible.  It  forms  no 
known  compounds.  It  is  admirably  adapted  for  filling 
balloons  and  dirigibles,  and  during  the  latter  part  of  the 
war  the  United  States  was  making  great  efforts  at  dis- 
covering some  method  of  preparing  it  in  commercial  quan- 
tities. Not  until  too  late  was  such  a  method  devised.  It 
is  still  a  secret  of  the  war  department. 

Exercises  for  Review 

1.  Name   some   of   the   gases   discovered   during   the   latter   part 
of  the  eighteenth  century  and  the  names  applied  to  them.     Why 
were  they  given  such  names? 

2.  Name  the  five  components  of  the  air.     Give  their  proportions 
by  volume  and  by  weight.     In  what  condition  are  they,  free  or  com- 
bined? 

3.  Give  three  or  four  proofs  that  the  air  is  a  mixture. 

4.  What  is  meant  by  diffusion  of  gases?     What  effect  does  dif- 
fusion have  on  the  homogeneity  of  the  air? 

5.  What  is  the  use  of  oxygen  to  the  human  body?    Why  are  most 
aquatic   animals   cold  bJooded?     Why   is  the   whale  not?     Explain 
how  the    body  is  warmed. 

6.  How  much  oxygen  is  removed  from  the  air  at  each  respira- 
tion?    How  many  cubic  feet  per  minute   are  needed  for  an  indi- 
vidual? 


THE    ATMOSPHERE  83 

7.  Of  what  use  is  the  nitrogen  of  the  air  to  the  body?     How  arc 
the  muscles  repaired?     Describe  the  nitrogen  cycle. 

8.  How  are   legumes   different  from   most   other   plants?     What 
gives  them  this  power? 

9.  What  do  considerable  quantities  of  carbon  dioxide  in  a  room 
indicate?     Is  it  deleterious  to  health? 

10.  Describe  the  carbon  cycle  between  plants  and  animals.    What 
use  do  plants  make  of  carbon?     Of  what  use  to  animals? 

11.  What    governs    the    amount    of    moisture    the    air    can   hold? 
What  is  meant  by  saturated  air?     How  much  more  moisture  can 
air  at  ordinary  room  temperature  hold  than  at  zero? 

12.  Why  is  a  humid  atmosphere  oppressive  in  summer? 

13.  What  effect   does  an   excessively  dry  atmosphere  have  upon 
the  body? 

14.  Give  some  methods  of  increasing  the  humidity  in  the  home 
in  winter. 

15.  Give  the  principle  underlying  the  liquefaction  of  air.     What 
is  a  Dewar  bulb? 

16.  Describe  liquid  air. 

17.  How  did  argon  come  to  be  discovered?     Who  was  first  to  at- 
tempt its  discovery?     Who  finally  discovered  it? 

18.  How  did  helium  receive  its  name?     Where  is  it  found  upon 
the  earth?     Of  what  special  value  will  it  be  in  large  amounts? 


CHAPTER  VI 

GASES  AND  SOME  GAS  LAWS 

Outline — 

States  of  Matter 

Charles'  Law  and  Absolute  Zero 

Applications  of  the  Law 
Boyle's  Law 

Correction  for  Changes  in  Temperature  and  Pressure 
Aqueous  Tension 
Deductions  from  these  Gas  Laws 

(«)    The  Molecular  Theory 

(&)   Molecular  Motion 

(c)   Gas  Pressures 
The  Atomic  Theory 
The  Corpuscular  Theory 
Atomic  and  Molecular  Weights 
Avogadro  's  Hypothesis 
Atomic  Structure  of  Molecules 
Determination  of  Molecular  Weights 
Gram  Molecular  Weight 

1.  States  of  Matter. — We  are  familiar  with  water  in 
three  conditions:  solid — ice;  liquid — water;  gas,  as 
steam.  It  has  been  stated  in  preceding  chapters  that 
oxygen,  hydrogen  and  other  gases  may  also  exist  in 
these  three  states.  There  are  two  forces  present  in  ev- 
ery body:  cohesion,  an  attractive  force,  tending  to  hold 
its  particles  together,  and  heat,  a  repellant  force,  tend- 
ing to  expand  it,  or  to  separate  its  particles.  Hence,  when 
heat  is  applied,  first  the  body  expands,  then  if  capable 
of  doing  so,  it  melts,  and  on  the  continued  addition  of 
heat  the  liquid  vaporizes  with  very  great  expansion. 
Removal  of  the  heat  reverses  the  process.  In  gases, 
therefore,  the  repellant  force  is  in  the  ascendancy ;  in 

S4 


GASES    AND    SOME    GAS    LAWS 


85 


solids,  the  cohesive  force.  Solids  and  liquids  upon  being 
heated  expand  very  irregularly ;  but  gases  are  practi- 
cally constant  and  their  behavior  is  described  by  cer- 
tain clearly  defined  laws. 

2.  Charles'  Law. — Experiment  shows  that  any  gas  if 
heated  from  0°  C.  to  1°  above,  expands  1/273  of  its  vol- 
ume at  zero.  Thus,  if  at  the  beginning  there  were  273 
c.c.,  at  1°  C.  there  would  be  274  c.c. ;  at  10°  C.  283  c.c. ; 
at  100°,  373  c.c.  Likewise,  if  cooled  below  zero,  at 


373-H  Boilinj  Point 


[-459- 
( 


Freezing  Pi. 


o- 
I 


Fig.  21. — Comparison  of  thermometers. 


- 10°  C.,  there  would  be  263  c.c.  at  100°  below,  173  c.c. 
Theoretically,  therefore,  if  a  gas  were  cooled  273°  below 
zero  its  volume  would  have  decreased  to  zero.  But  all 
gases  become  liquids  before  reaching  this  temperature; 
oxygen  at  -182.5°,  hydrogen  at  -252.6°,  helium  at 
-268.5°  and  thereafter  the  contraction  is  very  slight 
for  each  degree.  The  point,  273°  below  zero  is  known  as 
absolute  zero.  While  it  does  not  mean  the  elimination  of 
the  substance,  for  that  is  unthinkable,  it  may  be  assumed 


86  APPLIED    CHEMISTRY 

to  mean  the  temperature  at  which  there  is  no  longer  any 
heat  in  the  body.  In  the  liquefaction  of  helium,  that 
point  has  been  very  nearly  reached.  It  must  be  seen 
then  that  the  volume  of  a  gas  varies  as  the  absolute 
temperature.  Charles'  law  states  this  fact  thus:  The 
volume  of  a  gas,  pressure  remaining  constant,  increases 
or  decreases  directly  as  the  absolute  temperature.  The 
absolute  thermometer  is  not  a  manufactured  article,  but 
its  degrees  are  the  same  as  on  the  Centigrade  scale,  and 
it  must  be  used  in  all  problems  involving  Charles '  law ; 
hence  Fig.  21  is  given  to  make  the  method  clear.  Thus 
the  boiling  point  of  water  would  be  373°  absolute  and  of 
melting  ice  273°  absolute. 

3.  Value  of  Charles'  Law. — Gases  for  the  sake  of  con- 
venience are  measured  in  volumes,  but  as  they  change 
greatly  under  varying  conditions  some  standard  must 
be  adopted.  For  temperature  this  is  the  freezing  point 
of  water — zero  Centigrade.  However,  as  in  actual  work 
gases  are  seldom  obtained  at  this  temperature,  their 
volume  must  be  calculated  from  the  measured  volume. 
Knowing  that  they  increase  1/273  for  every  degree 
raised  above  zero,  this  is  not  difficult.  Putting  Charles' 
law  into  a  proportion  we  have 

V  :  V  ::T  :  T' 

In  which  V  is  the  original  volume  and  V  the  new  vol- 
ume, while  T  is  the  original  temperature,  absolute,  and 
T'  the  new  temperature  absolute.  In  the  form  of  an 
equation  this  reads, 

VT'  =  V'T 

from  which  either  volume  or  temperature  may  be  calcu- 
lated, knowing  the  other  factors.  To  make  the  process 
clear,  suppose  we  have  in  the  laboratory  a  bottle  hold- 


GASES   AND   SOME   GAS   LAWS  87 

ing  800  c.c.  of  oxygen,  with  the  temperature  15°  C.  and 
without  any  change  in  pressure  the  temperature  was 
raised  to  22°.  It  is  desired  to  know  the  new  volume. 
Changing  15°  C.  and  22°  C.  to  absolute  temperatures, 
we  have  273  +  15  =  288  and  273  +  22  ==  295.  Substi- 
tuting we  have 

800x295=V'x288 

800  x  295 

288 

from  which  the  value  of  V,  or  the  volume  at  22°  will  be 
known. 

4.  Boyle's  Law.  —  It  was  formerly  believed  that  liquids 
and  solids  could  not  be  compressed;  it  is  known  now, 
however,  that  they  may  be,  but  as  is  true  in  variation  of 
temperature  they  obey  no  law.  Gases,  on  the  other 
hand,  are  practically  constant,  a  fact  which  was  dis- 
covered by  Robert  Boyle  and  formulated  by  him  in  this 
law:  The  volume  of  any  gas,  provided  the  temperature 
remains  constant,  varies  inversely  as  the  pressure.  In- 
versely means  that  if  the  pressure  be  increased  the  volume 
is  diminished  correspondingly  and  if  the  pressure  be  de- 
creased the  volume  increases  in  the  same  ratio.  Put  into 
mathematical  form  it  is  stated  thus  : 

V  :  V  :  :  P'  :  P 

in  which  V  and  V  have  the  same  signification  as  stated 
under  Charles'  law  and  P  and  P'  are  the  original  and 
new  pressures  respectively.  In  the  form  of  an  equation 
the  proportion  becomes 


which  leads  to  another  statement  of  the  law,  thus:  The 
product  of  the  volume  of  any  gas  multiplied  by  its  pres- 
sure, alivays  assuming  that  the  temperature  is  constant, 
is  a  constant  quantity.  To  illustrate,  suppose  we  have 


88 


APPLIED    CHEMISTRY 


200  c.c.  of  oxygen  in  a  bottle  at  15  pounds'  pressure  to 
the  square  inch.  The  product  of  the  volume  and  pres- 
sure, VxP,  or  200x15,  is  3,000.  If  the  pressure  be 
doubled,  according  to  Boyle's  law,  the  volume  now  would 
be  100.  The  product  of  V  by  P',  or  100  x  30  is  3,000, 
the  same  as  before.  Hence  the  statement  that  the  vol- 
ume of  any  gas  multiplied  by  its  pressure  is  always  equal 


Fig.   22. — Aneroid  barometer. 

to  its  volume  at  any  other  time  multiplied  by  the  pressure 
at  that  time;  in  other  words,  the  product  is  a  constant 
quantity. 

5.  Pressures,  How  Stated. — In  most  practical  prob- 
lems involving  Boyle's  law  the  changes  are  those  of  at- 
mospheric pressure  only.  The  amount  of  such  pressure 
is  obtained  by  the  use  of  the  barometer,  which  for  the 


GASES    AND    SOME    GAS    LAWS  89 

sake  of  convenience  is  read  in  units  of  length  and  not 
weight.  In  the  aneroid  barometer,  shown  in  Fig.  22,  the 
figures  on  the  dial  indicate  inches,  while  the  smaller 
divisions  are  millimeters  of  which  practically  760  equal 
30  inches.  In  the  mercurial  barometer  at  sea  level, 
the  pressure  of  the  air  supports  a  column  of  mercury 
30  inches  in  height  or,  in  other  words,  the  weight  of  30 
inches  of  mercury.  But  as  the  iveiylit  of  28  inches  of 
mercury  would  have  the  same  mathematical  relation  to 
the  ivcight  of  30  inches  of  mercury  as  28  inches  to  30 
inches,  and  as  length  can  be  read  immediately  from  the 
barometer,  in  all  problems  it  is  customary  to  use  linear 
units,  and  those  of  the  metric  system  ;  that  is,  millimeters 
or  centimeters.  To  illustrate:  Suppose  the  barometer 
reads  750  mm.  and  we  have  in  a  bottle  standing  over 
mercury  500  c.c.  of  gas,  and  wish  to  know  the  volume  at 
standard  pressure,  which  means  pressure  at  sea  level,  or 
760  mm.  pressure.  Substituting  in  the  formula, 

VP  ==  V'P', 

we  have        500  x  750  =  V  x  760 

500  x  750 

~~ 


in  which  V  will  be  the  true  volume  at  one  atmosphere's 
pressure. 

6.  Corrections    for    Pressure    and    Temperature.  —  In 

practical  work  often  both  pressure  and  temperature 
have  changed  during  the  time  of  an  experiment.  In 
such  cases  calculation  must  be  made  to  correct  both. 
This  may  be  done  in  two  steps,  by  finding  the  volume 
resulting  from  one  change,  either  pressure  or  tempera- 
ture, and  then  using  this  in  the  other  equation.  In  fact 
beginners  may  find  all  such  problems  easier  if  solved  by 
analysis  instead  of  by  use  of  formula  given.  At  any 


90  APPLIED    CHEMISTRY 

rate  the  method  has  the  advantage  of  appealing  to  the 
reasoning  powers  at  every  step  and  on  that  account 
is  good.  It  must  be  evident  that  increased  pressure 
would  cause  decreased  volume.  Hence  the  original 
volume  must  be  multiplied  by  a  fraction  greater  or  less 
than  one  as  the  change  in  pressure  would  cause  increase 
or  decrease  in  volume.  Thus,  if  we  have  500  volumes  of 
gas  at  760  mm.  pressure  and  wish  to  know  what  it  would 
be  at  780,  we  must  ask  ourselves,  whether  the  volume  is 
increased  or  decreased.  As  the  pressure  is  greater,  the 
volume  would  be  less:  hence  the  original  500  cubic  centi- 
meters must  be  multiplied  by  760/780  which  will  give  a 
result  less  than  500.  In  the  same  way  Charles'  Law  may 
be  applied.  Increase  in  temperature  causes  increase  in 
volume.  Thus,  remembering  that  absolute  temperatures 
are  always  used,  suppose  we  have  500  c.c.  of  gas  at  zero 
Centigrade  and  wish  to  know  its  volume  at  20  degrees 
above:  we  must  first  change  Centigrade  readings  into 
Absolute.  In  this  case  they  would  be  respectively  273 
and  293.  As  the  volume  is  increased  the  500  c.c.  must 
be  multiplied  by  the  fraction  293/273  which  will  give  a 
value  greater  than  500.  In  case  both  temperature  and 
pressure  change,  the  result  obtained  in  one  of  the  above 
operations  must  be  used  as  the  original  volume  for  the 
next. 

It  is  somewhat  simpler,  however,  to  use  a  combined  for- 
mula, VPT'  =  V'P'T, 

in  which  the  letters  mean  as  previously  stated.  To  il- 
lustrate its  use :  Suppose  we  have  500  c.c.  of  hydrogen 
over  a  trough  of  mercury  at  a  temperature  of  21°  C. 
with  the  barometer  reading  740  mm.  It  is  desired  to 
know  the  volume  at  standard  conditions,  that  is  zero 
Centigrade  and  760  mm.  pressure.  Substituting  in  the 
formula  VPT'  =  V'P'T,  we  have 


GASES   AND   SOME   GAS   LAWS 


91 


500  x  740  x  (273'  +  0)  =  V  x  760  x  (273  +  21) 
500  x  740  x  273 


In  a  similar 
or  any  other 


760  x  294 

The  value  of  V  will  be  the  true  volume. 
way  we  might  find  the  value  of  T'  or  P' 
factor  provided  the  others  were  known. 

7.  Correction  for  Water  Vapor.  —  In  the  laboratory 
gases  are  usually  collected  over  water  and  hence  con- 
tain some  vapor.  To  learn  their  true  volume  at  standard 
conditions,  correction  must  be  made  for  this.  It  has  been 
found  that  at  any  given  temperature  the  vapor,  passing 
off  from  an  enclosed  vessel  of  water,  will  exert  a  definite 
pressure,  always  the  same  for  that  particular  tempera- 


AIR  PRESSURE 


Fig.    23. — Illustrating    pressure    of    water    vapor. 

ture.  In  Fig.  23',  suppose  we  have  a  volume  of  gas  with 
the  water  at  the  same  level  inside  and  without  the  bot- 
tle. Obviously  the  pressure  within  and  without  must 
be  the  same.  On  the  outside  the  pressure  is  due  to  the 
weight  of  the  air  resting  upon  the  water.  Inside,  the 
pressure  results  mainly  from  the  gas  enclosed!,  buit 
partly  from  the  vapor  mixed  with  the  gas.  To  know 
the  real  pressure  of  the  gas,  that  of  the  vapor,  which  is 
spoken  of  as  aqueous  tension,  must  be  subtracted  from 
the  total  pressure.  To  illustrate :  Suppose  the  gas  in  the 
bottle  measures  900  c.c.  and  the  barometer  reads  750  mm., 
and  the  thermometer,  20°  C.  The  aqueous  tension  at  20° 


92  APPLIED    CHEMISTRY 

is  about  17  mm. ;  hence,  the  pressure  which  the  gas  within 
the  bottle  is  exerting  is  750  minus  17  or  733  mm.  Then, 
if  it  were  required  to  find  the  true  volume  at  standard 
pressure,  the  following  substitution  would  be  made  in 
the  formula,  VP  ==  V'P' 

900  x  (750 -17)  =  Y'x760 

The  following  table  gives  the  aqueous  tension  for  a  short 
range  of  ordinary  room  temperatures. 


Temperature 

Aq.  Tension 

Temperature 

Aq.  Tension 

16°  C. 
17 
18 
19 
20 

13.54  mm. 
14.42 
15.36 
16.35 
17.39 

21°  C. 

22 
23 
24 
25 

18.49  mm. 
19.66 
20.88 
22.18 
23.55 

8.  Application  of  these  Laws. — The  gas  in  most  cities 
is  furnished  by  some  company  which  is  required  by  or- 
dinance to  maintain  a  certain  pressure,  say  6  or  8  inches, 
water  pressure.  If  instead  of  doing  this  the  company 
allow  the  pressure  to  drop  to  4  or  2  inches  or  any  lower 
pressure  than  that  specified,  it  is,  according  to  Boyle's 
law,  furnishing  the  consumer  an  expanded  gas ;  therefore, 
while  the  meter  registers  the  larger  amount  the  consum- 
er only  has  the  value  contained  in  the  real  volume.  It 
should  be  stated,  however,  that  as  the  6  or  8  inches  re- 
quired is  necessarily  the  pressure  in  addition  to  one  at- 
mosphere or  30  water  feet,  a  drop  of  4  inches  is  not  rel- 
atively large.  Nevertheless,  consumers  should  be  fur- 
nished gas  by  the  number  of  heat  units  contained  and 
not  by  volume.  The  aeronaut  must  observe  these  gas 
laws  in  filling  his  balloon.  Too  great  initial  pressure, 
when  he  has  ascended  into  a  rarer  atmosphere,  and 
bright  sunlight,  may  result  in  such  increased  pressure 
through  expansion  from  the  heat  of  the  sun  as  to  burst 
the  balloon.  On  the  other  hand,  too  low  initial  pressure, 


GASES   AND   SOME   GAS   LAWS  03 

when  night  comes,  with  the  great  drop  of  temperature  in 
the  upper  air  may  cause  such  contraction  of  volume  that 
the  buoyancy  of  the  balloon  will  110  longer  support  the 
attendant  weight. 

9.  Some  Deductions. — Cooling  or  heating  a  given  vol- 
ume of  gas  does  not  change  its  weight.  Compressing, 
or  the  reverse,  likewise,  has  no  effect  upon  the  weight; 
therefore,  obviously  by  any  of  these  changes  we  have 
not  affected  the  real  quantity  of  the  gas.  At  sea  level, 
the  pressure  of  the  air  per  square  inch  of  surface  is  about 
15  pounds.  Now  it  is  possible  by  modern  appliances  to 
obtain  pressures  approximating  150,000  pounds  to  the 
square  inch.  To  some  gases,  such  pressures  as  these  may 
be  applied  and  they  are  still  gases  unless  the  tempera- 
ture is  also  greatly  decreased:  according  to  Boyle's 
law  the  volume  has  been  decreased  to  one  ten-thousandth 
part  of  what  it  was  originally.  In  other  words,  the  par- 
ticles constituting  the  gas  have  been  moved  closer  to- 
gether, so  that  now  they  are  only  one  ten-thousandth 
part  as  far  from  each  other  as  they  were  at  the  begin- 
ning. Under  moderate  pressures,  as  we  have  seen,  all 
gases  behave  alike ;  hence,  there  can  be  only  one  deduc- 
tion and  that  is  that  all  gases  are  composed  of  particles 
not  touching  each  other ;  really,  of  particles  at  relatively 
great  distances  from  each  other.  As  all  liquids  may 
likewise  be  compressed,  though  but  slightly  and  irreg- 
ularly, their  particles  also  must  not  be  contiguous.  This 
may  be  shown  to  be  true  by  a  simple  experiment.  If 
a  liter  cylinder  be  half  filled  with  alcohol  and  then  a 
like  amount  of  water  cautiously  introduced  beneath  the 
alcohol  by  means  of  a  pipette,  at  first  there  will  be  1,000 
c.c.  of  the  two  unmixed  liquids  (Fig.  24).  Now,  if  by  a 
stirring  rod  they  are  thoroughly  mixed,  the  volume  will 
be  found  to  have  decreased  about  10  per  cent.  Like- 


94 


APPLIED    CHEMISTRY 


wise,  considerable  quantities  of  various  solids  like  salt, 
or  sugar  or  alum  may  be  dissolved  in  a  given  volume  of 
water  without  increasing  the  volume  to  any  great  ex- 
tent. It  is  like  pouring  a  pint  of  sand  upon  a  quart  of 
coarse  shot.  By  adding  the  sand  cautiously  with  fre- 
quent shaking,  the  sand  may  be  largely  introduced  into 
the  bottle  of  shot.  About  500  liters  of  hydrogen  chlo- 
ride gas  may  be  passed  into  a  liter  of  ice  water  with 
comparatively  little  increase  in  volume,  and  of  ammonia, 


Before  mixing        A-fic 


Fig.   24. — Contraction   of  volume  on  mixing  two   liquids. 

more  than  1,000  may  be  thus  introduced.  Experiments 
with  solids  many  years  ago  showed  that  they  were  po- 
rous. Metal  globes  filled  with  water  were  subjected  to 
pressure  and  were  flattened.  The  liquid  was  forced 
through  the  metal  and,  appearing  as  drops  upon  the  out- 
side, showed  that  there  were  spaces  between  the  particles 
of  the  solid  through  which  the  water  particles  could 
pass.  Another  experiment  made  some  years  ago  in  Lon- 
don proves  not  only  the  same  thing,  but  that  the  par- 


GASES   AND   SOME   GAS   LAWS  95 

tides  of  a  solid  are  even  free  to  move  about  from  one 
place  to  another.  Some  cylinders  of  lead  were  placed 
upon  sheets  of  gold  and  allowed  to  remain  thus  for  four 
years.  Analyses  were  then  made  of  the  lower  end  of 
the  lead  cylinders  and  the  gold  was  found  to  have  pene- 
trated them  to  a  distance  of  8  mm. 

10.  Molecular  Theory,— The  foregoing  and  many  other 
experiments  have  led  scientists  to  believe  as  conclusive 
that  matter  is  not  continuous,  but  made  up  of  minute 
particles  not  touching  each  other.  To  these  they  have 
given  the  name  of  molecules.  They  are  the  smallest  divi- 
sion of  matter  possible  without  destroying  the  identity 
of  the  substance.  Thus  a  molecule  of  water  or  of  salt, 
would  possess  all  the  essential  characteristics  of  the  larger 
mass  of  water  or  salt.  In  solids  these  molecules  are  close 
together;  in  liquids  farther  apart,  and  in  gases  at  rela- 
tively very  great  distances.  To  illustrate:  In  a  gas  un- 
der ordinary  room  conditions,  the  individual  molecules 
are  relatively  farther  apart  than  is  the  moon  from  the 
earth,  when  diameters  are  considered.  The  diameter  of 
the  earth  is  about  8,000  miles,  so  that  the  distance  of  the 
moon  is  only  about  30  times  the  diameter  of  the  earth. 
Many  gases  may  be  compressed  thirtyfold  and  still  remain 
gases,  showing  that  their  molecules  are  still  far  apart.  A 
gas  which  may  be  compressed  by  ten  thousand  atmos- 
pheres would  have  its  molecules  brought  ten  thousand 
times  nearer  together  than  they  were ;  ten  thousand  times 
the  diameter  of  the  earth  would  approach  in  distance  that 
of  the  sun.  from  the  earth.  This  gives  some  idea  of  the 
real  distance  of  the  molecules  from  each  other.  A  bottle 
full  of  hydrogen,  as  we  say,  is  really  a  bottle  with  com- 
paratively few  particles  of  the  gas  at  relatively  great 
distances  from  each  other.  It  is  difficult  for  the  human 
mind  to  form  any  conception  of  the  infinitesimal  size  of 


96  APPLIED    CHEMISTRY 

a  molecule.  Someone  has  said  that  if  a  buckshot  were  mag- 
nified to  the  size  of  the  earth  and  the  composing  mole- 
cules likewise  were  magnified,  they  would  then  be  some- 
thing like  the  size  of  the  buckshot.  Lord  Kelvin,  the 
great  English  scientist,  has  shown  that  in  solids,  the  dis- 
tance from  the  center  of  one  molecule  to  the  center  of 
the  next  is  not  less  than  one  five-hundred-millionth  of  an 
inch.  So  if  they  were  actually  touching,  their  diameters 
would  be  one  five-hundred-millionth  of  an  inch.  If  their 
distances  apart  equal  the  diameter  of  the  molecule,  then 
their  diameters  would  be  one  half  as  great  or  one  billionth 
of  an  inch.  To  count  the  number  possible  of  lying  upon 
a  line  1  inch  long,  at  the  rate  of  one  per  second,  would 
require  nearly  39  years  of  360  days  each,  ten  hours 
per  day.  Automobiles,  equal  in  number,  with  a  wheel-base 
of  120  inches  spaced  10  feet  apart  would  form  a  proces- 
sion reaching  a  little  more  than  seventy-five  times  around 
the  earth. 

11.  Molecules  Not  at  Rest. — At  several  times  in  pre- 
ceding chapters  it  has  been  necessary  to  refer  to  the  fact 
that  the  particles  of  gases  or  liquids  are  not  at  rest.  The 
experiment  of  Roberts-Austin  of  the  gold  leaf  under 
the  lead  cylinders  shows  the  same  for  solids.  Molecules 
are  not  like  dust  particles  in  the  air.  These  soon  settle 
when  the  existing  cause  is  removed,  but  not  so  with  mole- 
cules. According  to  Boyle's  law,  when  the  pressure  is 
removed  from  gases,  they  tend  to  expand  indefinitely, 
so  that  a  pint  of  any  gas  opened  into  a  vacuum,  no  mat- 
ter how  large,  would  be  quickly  distributed  throughout 
the  entire  space.  The  passage  of  a  gas  throughout  the 
space  occupied  by  another  or  of  one  liquid  through  an- 
other has  been  spoken  of  as  diffusion,  and  can  be  ex- 
plained only  on  the  assumption  that  molecules  possess  the 
inherent  power  of  motion  and  that  they  are  continuously 


GASES   AND   SOME   GAS   LAWS  97 

in  motion.     This  is  known  as  the  kinetic  theory  of  gases. 

12.  Gas  Pressure,  Result  of  This  Motion. — By  methods 
not  necessary  to  be  discussed  here,  it  has  been  learned 
that  the  average  velocity  with  which  these  gas  molecules 
are   moving   is   very    considerable.      With   the    lightest 
gases  such  as  hydrogen,  it  is  several  miles  per  second. 
Naturally,   therefore,   the  numerous  successive   impacts 
upon  the  wall  of  any  containing  vessel  must  produce  a 
pressure.     Such  is  the  cause  of  the  pressure  exerted  by 
any  gas  upon  the  inside  of  the  containing  vessel  and 
is  simply  its  resistance  to  being  compressed.     It  is  not 
the  same  as  the  air  pressure  upon  a  surface  at  any  par- 
ticular altitude,  for  that  is  merely  the   weight   of  the 
column  of  air  supported  at  that  point.     In  discussing 
hydrates  in  Chapter  II,  it  will  be  remembered  that  a 
manometer  tube  was  mentioned  as  being  used  to  show 
the  pressure  of  the  water  vapor  at  different  tempera- 
tures.    It  is  simply  the  impacts  of  the  molecules  of  va- 
por upon  the  surface   of  the   mercury  that  push   it  up 
into  the  bent  tube.     Similarly,  when  we  pump  air  into 
an  automobile  tire  and  the  pressure  gauge  registers  an 
increase  from  40  to  80  pounds,  we  have  simply  doubled 
the  quantity  of  air  in  the  tire  so  that  the  number  of  im- 
pacts per  second  has  been  doubled. 

13.  The  Atomic  Theory. — John  Dalton,  a  scientist  who 
died   in   1844,   showed   conclusively   that   while   the   as- 
sumption of  the  molecular  structure  of  matter  satisfies 
most  of  the  needs  of  physical  phenomena,  it  does  not 
explain  many  things  in  chemistry.     He  proposed  what 
is  now  known  as  the  atomic  theory.    The  most  important 
features  of  this  theory  are,  first,  that  molecules  are  cap- 
able  of   division  into   still  smaller  particles,   which  he 
called  atoms.     The  word  means  not  able  to  be  divided, 
and  up  to  comparatively  recent  years  the  atom  has  been 


98  APPLIED    CHEMISTRY 

regarded  as  the  smallest  possible  division  of  matter.  It  is 
usually  defined  as  the  smallest  particle  of  matter  capable 
of  entering  into  a  chemical  reaction.  Second,  it  is  as- 


Fig.    25. — Dalton,   who   proposed    the   atomic   theory   of   matter. 

sumed  by  this  theory  that  the  atoms  of  each  particular 
element  have  a  definite  and  fixed  weight.  Hence,  when 
they  enter  into  combination,  one  or  more  of  these  defi- 
nite weights  must  be  used.  Third,  the  weight  of  an  atom 


GASES    AND    SOME    GAS    LAWS  99 

of  each  clement  is  different  from  that  of  every  other 
element;  fourth,  chemical  action  takes  place  between 
atoms  and  not  between  larger  masses.  Accordingly,  to 
use  a  somewhat  unscientific  illustration,  matter  is  tied  up 
by  nature  in  small  packages  or  bundles,  and  when  these 
are  used  together  in  chemical  reactions  it  becomes  neces- 
sary to  use  one,  two  or  more  of  the  packages. 

14.  The  Corpuscular  Theory.— As  stated  just  above, 
the  word  atom  means  unable  to  be  divided.     Recently, 
however,  it  has  been  found  that  certain  substances,  ra- 
dium for  example,  are  able  to  give  off  particles  with  a 
velocity  nearly  the  same  as  that  of  light  and  with  a  mass 
about  one-thousandth  part  that  of  the  hydrogen  atom. 
These  particles  are  called  electrons  or  corpuscles,  and  are 
found  to  carry  a  negative  charge  of  electricity.    Further, 
electrons,  no  matter  what  their  origin,  all  seem  to  be  of 
the  same  mass.     Prof.  J.  J.  Thompson  suggests  that  just 
as  the  molecules  of  a  gas  are  at  great  distances  from  each 
other,   so  are  these  electrons  in  the  atom,  and  he  com- 
pares them  to  a  thousand  dots   (.)   scattered  throughout 
a  church  building.    The  work  of  Thompson  and  of  other 
experimenters  seems  to  admit  of  no  doubt  as  to  the  truth 
of  the  theory,  yet  it  in  no  way  lessens  the  value  or  de- 
stroys the  probability  of  the  truth  of  the  atomic  theory. 
Chemical  action  is  between  or  among  atoms,  and  the  ex- 
istence of  electrons  simply  aids  in  explaining  many  phe- 
nomena observed  which  otherwise  is  not  possible. 

15.  Atomic  Weights. — It  was  stated  above  that  Dai- 
ton's  atomic  theory  assumes  that  the  atoms  of  each  ele- 
ment have  a  particular  and  definite  weight.     Naturally, 
it  will  be  understood  that  to  weigh  anything  so  small  as 
an  atom  is  impossible.    Hence,  atomic  weights  are  merely 
relative  weights.    As  hydrogen  is  the  lightest  of  all  sub- 
stances, it  would  be  presumed  that  its  atom  would  be 


100  APPLIED   CHEMISTRY 

used  as  a  standard  for  measuring  others.  This  was  at 
first  done  and  the  term  microcrith  was  applied  to  the  unit. 
On  this  basis  the  weight  of  the  oxygen  atom  is  approxi- 
mately 16,  more  accurately,  15.998.  It  was  found,  fur- 
ther, that  if  the  hydrogen  atom  was  assumed  to  have  a 
weight  of  one  microcrith,  the  atomic  weights  of  a  large 
number  of  other  elements  differ  considerably  from  whole 
numbers.  On  the  other  hand,  if  oxygen  is  assumed  as 
weighing  exactly  16  microcriths,  which  will  give  hydro- 
gen a  weight  of  1.008,  a  very  considerable  number  of  the 
other  elements  will  have  atomic  weights  of  either  whole 
numbers  or  closely  approaching  these.  On  account  of  the 
advantage  which  this  affords  in  accurate  chemical  calcu- 
lations, it  is  regarded  as  preferable.  Tables  of  atomic 
weights  are,  therefore,  usually  given  on  the  basis  of  the 
oxygen  atom  having  a  mass  of  16  microcriths.  To  define 
atomic  weight,  therefore,  we  would  say  that  it  is  the  weight 
in  microcriths  of  an  atom  of  any  element  as  compared 
with  the  oxygen  atom  whose  mass  is  16  microcriths,  or  with 
hydrogen,  1.008  microcriths.  Thus  when  we  say  sulphur 
has  an  atomic  weight  of  32,  we  mean  in  the  form  of  va- 
por it  is  twice  as  heavy  as  oxygen  or  nearly  32  times  as 
heavy  as  hydrogen.  (See  page  441.) 

16.  Molecular  Weights. — The  molecular  weight  of  a 
substance  is  the  sum  of  the  weights  of  all  the  atoms 
found  in  a  molecule  of  that  particular  substance.    It  will 
be  shown  later  that  a  molecule  of  water  contains  two 
atoms  of  hydrogen  and  1  of  oxygen.    Adding  the  weights 
of  two  atoms  of  hydrogen  and  1  of  oxygen,  gives  for  water 
a  molecule  weight  of  18.     Thus,  knowing  the  composition 
of  the  molecule  of  any  substance,  we  may  determine  its 
molecular  weight. 

17.  Avogadro's  Hypothesis.— The  great  Italian  phys- 
icist  in   1811   formulated   the   hypothesis   which   bears 


GASES    AND    SOME    GAS    LAWS 


101 


his  name.  It  is,  Equal  volumes  of  all  gases  under  the  same 
pressure  and  temperature,  contain  the  same  number  ,of 
molecules.  To  illustrate,  this  simply;  ^atoS/that  L£*]ffc.c. 
of  hydrogen  contain  a  thousand  ,moh;cnle,'v on/J, qi'w  oxygen, 
or  any  other  gas  would  contain  the  gaftjje.,  : No  absolute  ex: 
perimental  proof  of  its  truth  has  been  furnished,  but 
similar  changes  of  volume  for  all  gases  under  varying 
temperatures  and  pressure,  as  well  as  many  other  ob- 


Fig.   26. — A   simple   eudiometer   connected   to   induction   coil,   marked   I. 

served    facts,    are    strong    presumptive    evidences    of    its 
truth. 

18.  Numbers  of  Atoms  in  a  Molecule. — Assuming  the 
truth  of  the  hypothesis  just  given,  it  is  possible  to  as- 
certain the  number  of  atoms  in  a  molecule  of  the  various 
gaseous  elements  or  of  those  which  may  be  vaporized. 
For  example,  it  has  been  found  that  water  consists  of 
two  volumes  of  hydrogen  to  one  of  oxygen.  If  the  con- 
verse of  the  experiment  described  in  Chapter  II  be  car- 


102  APPLIED    CHEMISTRY 

ried  out  with  an  apparatus  called  a  eudiometer,  shown 
in  Fig.  26,  and  correction  be  made  for  temperature,  this 
fact?  is  .Obsertedi  ;/»  \ 


??  "°£  JtJ$rogei\  exploded  with  1  of  oxygen  produce  2  vol- 
•   knifes  of  sic-Kin;,  or--  Cutting  it  more  concretely, 
20   c.c.   hydrogen  with   10   c.c.    oxygen  produce   20   c.c.    steam. 

The  experiment  shows  that  the  30  c.c.  of  mixed  gases 
when  combined  yield  only  20  c.c.  of  the  vapor,  there 
being  a  condensation  of  one-third.  Applying  Avoga- 
dro's  hypothesis,  supposing  there  are  20  thousand  mole- 
cules in  the  20  c.c.  of  hydrogen,  and  substituting  we 
should  have  — 

20  thousand   mol.  hydrogen  with  10  thousand  mol.   O.  produce   20 
thousand  mol.  steam  ; 

or, 
2  mol.  hydrogen  +  1  mol.  oxygen  give  2  mol.  steam. 

Now  it  must  be  admitted  as  true  that  each  molecule  of 
steam  contains  some  oxygen  ;  hence,  as  there  are  2  mole- 
cules of  steam  produced  for  every  molecule  of  oxygen, 
the  oxygen  molecule  must  have  been  divided  into  two 
parts.  Using  the  same  apparatus  and  substituting  chlo- 
rine for  oxygen,  but  using  equal  volumes  of  each  gas, 
the  experiment  may  be  repeated,  with  these  results: 

20  c.c.  hydrogen  +  20  c.c.  chlorine  give  40   c.c.  hydrogen  chloride. 

Here  it  will  be  noticed  that  although  chemical  change 
has  taken  place  the  volume  has  not  changed,  the  new 
substance  having  the  same  as  the  combined  volume  of 
the  mixed  gases.  Applying  Avogadro's  hypothesis  as 
before, 

2  mol.  hydrogen  4-  2   mol.  chlorine  give  4  mol.  hydrogen  chloride. 

Now  since  the  number  of  hydrogen  chloride  molecules 
is  double  that  of  the  hydrogen  molecules,  each  one  of 


GASES    AND    SOME    GAS    LAWS  103 

the  latter  must  have  been  broken  into  at  least  two  portions. 
Likewise  has  the  ehlorine  molecule.  Since  no  cases  have 
ever  been  observed  in  which  the  molecules  of  these  gases 
are  broken  into  more  than  two  parts,  it  is  assumed  that 
a  smaller  division  is  impossible  chemically  and  these 
particles  are  atoms.  With  the  exception  of  ozone,  which 
has  been  stated  as  being  a  peculiar  form  of  oxygen, 
with  three  atoms  to  the  molecule,  all  the  common  ele- 
mentary gases,  like  hydrogen  and  chlorine,  have  two 
atoms  to  the  molecule  and  are  said  to  be  diatomic.  Argon, 
helium,  and  the  other  rare  gases,  belonging  to  the  same 
family,  are  monatomic.  Mercury  and  some  other  metals 
are  likewise  monatomic,  while  phosphorus  and  arsenic  are 
tetratomic. 

19.  Gay-Lussac's  Law. — In  all  the   experiments   out- 
lined just  above  where  one  gas  combined  with  another, 
it  will  be  noticed  that  the  volumes  always  bore  some 
simple  relation  to  each  other.     When  weights  are  con- 
sidered, this  is  often  not  true.    For  example,  in  common 
salt  by  weight  chlorine  unites  with  sodium  in  the  pro- 
portion of  about  35.5  to  23.     In  volumes  it  will  be  seen 
that  exactly  two  of  hydrogen  combine  with  one  of  oxy- 
gen to  form  water ;  one  of  hydrogen  combines  with  one  of 
chlorine  to  produce  hydrogen  chloride,  and  three  of  hy- 
drogen with  one  of  nitrogen  to  form  ammonia.     This  has 
been  discovered  to  be  a  general  truth  and  has  been  form- 
ulated in  what  is  known  as  Gay-Lussac's  law.     It  is  usu- 
ally stated  thus:    The  volumes  of  gases  when  uniting  with 
each  other  chemically  and  of  the  gaseous  products  formed 
~by  the  union  may  always  l)C   expressed  in  small  whole 
numbers.    This  law  will  be  further  illustrated  in  the  fol- 
lowing chapter  in  some  problems  of  combustion. 

20.  Determination  of  Molecular  Weights. — It  has  been 
found  by  experiment  that  a  liter  of  hydrogen  weighs 


104  APPLIED    CHEMISTRY 

.0898  grams,  and  one  of  oxygen  1.429;  or,  in  larger 
amounts,  22.4  liters  of  hydrogen  weigh  2  grams  and 
the  same  volume  of  oxygen,  32  grams.  According  to 
Avogadro's  hypothesis,  since  there  are  the  same  num- 
ber of  molecules  of  each  gas  in  the  22.4  liters,  the  rela- 
tive weight  of  the  two  must  be  the  relative  weight  of 
the  two  molecules.  It  may  be  said,  in  fact,  that  22.4  liters 
of  any  gas  will  always  weigh  approximately  as  many 
grams  as  there  are  microcriths  in  the  molecular  weight 
of  that  gas.  It  has  been  stated  above  that  hydrogen  and 
oxygen  are  both  diatomic  gases  ;  hence,  since  their  atomic 
weights  are  1  to  16  respectively,  their  molecular  weights 
would  be  2  and  32  respectively  which  correspond  to  the 
weights  in  grams  given  above  for  22.4  liters.  Likewise, 
the  molecular  weight  of  carbon  monoxide  is  28,  and  22.4 
liters  weigh  approximately  28  grams.  This  fact  may  be 
used  to  determine  the  molecular  weight  of  various  gases. 
For  example,  22.4  liters  of  carbon  dioxide  weigh  approx- 
imately 44  grams;  hence,  the  molecular  weight  of  this 
gas  would  be  44. 

21.  Gram  Molecular  Weight. — The  molecular  weight 
of  any  substance,  stated  in  grams,  is  called  its  gram  mo- 
lecular weight.  Thus  the  molecular  weight  of  water  is 
18;  of  cane  sugar,  342;  hence,  18  grams  and  342  grams 
would  be  Respectively  gram  molecular  weights  of  these 
two  substances.  Sometimes  such  a  weight  is  spoken  of 
as  a  mol  or  a  molar  weight.  If  a  gram  molecular  weight 
of  various  gases  be  measured  under  standard  temperature 
and  pressure,  allowing  for  slight  variations  which  admit 
of  explanation,  the  volume  is  always  approximately  22.4 
liters.  Thus, 

Hydrogen,  2  grams  occupy  22.4  liters 
Oxygen,  32  grams  occupy  22.4  liters 
Nitrogen,  28  grams  occupy  22.4  liters 
Carbon  Dioxide,  44  grams  occupy  22.4  liters 


GASES    AND    SOME    GAS    LAWS  105 

Conversely,  therefore,  if  we  determine  the  weight  of  22.4 
liters  of  any  gas  we  have  a  means  of  knowing  approxi- 
mately its  molecular  weight.  This  method  often  serves 
in  checking  up  other  methods  of  finding  molecular  weights 
and  in  this  way  is  of  great  value. 

Exercises  for  Review 

1.  Name   the  throe   states   of  matter  and  the   two  forces  which 
govern  them. 

2.  State   Charles'   law.      Illustrate.      What   is   the   absolute   zero 
point?     How  did  it  come  to  be  adopted? 

3.  State  Boyle's  law.     What  is  meant  by  standard  pressure  and 
temperature? 

4.  What  is  the  formula  for  correcting  volumes  when  both  tem- 
perature and  pressure  change? 

5.  What  is  meant  by  aqueous  tension?     Would  it  be  used  when 
a  gas  is  collected  over  mercury?     Explain. 

6.  What  can  be  said  about  the  contiguity  of  matter?     Why  must 
this  conclusion  be  reached? 

7.  Give  some  experimental  proof  that  matter  is  not  continuous. 

8.  Wrhat  is  the  molecular  theory?     A  molecule?     Give  some  idea 
of  the  size  of  a  molecule ;  of  the  distance  they  are  apart  in  gases. 

9.  What  proofs  can  you  offer  that  molecules  are  not  at  rest? 

10.  What  gives  the  pressure  on  the  inside  of  a  tire  on  a  motor 
car?     If  you  double  the  quantity  of  air  already  in  a  tire  what  ef- 
fect upon  the  pressure?     Why? 

11.  Give  the  four  main  assumptions  of  the  atomic  theory.     What 
is  an  atom? 

12.  What  is  an  electron?     What  can  you  say  of  its  mass?     Does 
this  theory  destroy  the  truth  of  the  atomic?     Why? 

13.  What  is  meant  by  the  atomic  weight  of  an  element?     Illus- 
trate.    What  is  a  microcrith? 

14.  State  Avogadro's  hypothesis.     Of  what  use  is  it? 

15.  What  is  a  monatomic  molecule?     A  diatomic?     Name  some. 

16.  Give  one  method  of  determining  experimentally  the  molecu- 
lar weight  of  a  gas. 


CHAPTER  VII 

SYMBOLS  AND  FORMULAS 
Outline — 

The  Origin  of  Symbols 
Present  Use  of  Symbols 
Formulas 

(a)   Empirical 

(fr)   Structural 
Eadicals 
Equations 

1.  Origin  of  Symbols. — The  use  of  symbols  began  with 
the  alchemists  who  sought  thereby  to  render  unintelli- 
gible  the  notation   of   their   attempts   at   making   gold 
from  the  baser  elements.    Modern  chemists  have  found 
it  necessary  in  mathematical  calculations  and  in  vari- 
ous other  ways  to  use  short  methods  of  representing 
chemical   compounds   and   the    reactions   taking    place. 
Moreover,  chemical  symbols  as  now  used  are  intelligible 
to  all  chemists  the  world  over,  so  that  out  of  a  plan 
adopted  to  keep  secret  the  work  done  has  come  a  uni- 
versal language  read  by  all  chemists. 

2.  What  Are  Symbols?— A  symbol  is  a  letter  or  letters 
used  to  represent  a  single  atom  of  an  element.     Usually 
it  is  the  initial  letter,  but  as  this  is  the  same  for  a  number 
of  elements,  the  initial  letter  is  often  followed  by  some 
other  distinctive  one  of  the  word.     It  must  be  noted  that 
the  initial  letter  is  always  capitalized,  while  the  second, 
if  another  be  used,  is  not.     Thus  C  is  the  symbol  for 
carbon;  Ca  for  calcium;  Cd  for  cadmium;  Co  for  cobalt. 
Several  of  the  elements  receive  their  symbols  from  the 
Latin  or  some   other  foreign  language;   thus,   K  is  for 

106 


SYMBOLS    AND    FORMULAS  107 

potassium,  Kalium;  Na  for  sodium,  Natrium;  Ag,  silver, 
Argent-inn;  Hg  for  Mercury,  Hydrargyrum. 

3.  Formulas. — A  formula  is  a  combination  of  symbols 
representing  a  molecule  of  a  substance,  usually  that  of  a 
compound.  In  its  broadest  sense  it  may  represent  the 
molecule  of  an  element.  Thus,  HC1  is  the  formula  for 
hydrogen  chloride,  while  HH,  usually  written  H2  is  the 
formula  for  a  molecule  of  hydrogen.  To  represent  the 
formula  of  a  compound  naturally  the  number  of  atoms 
of  each  element  contained  must  be  shown.  If  there  be 
more  than  one  of  any  of  them,  that  fact  is  indicated  by 
a  small  figure  written  at  the  right  and  slightly  below  the 
symbol  to  be  multiplied.  Thus,  water  is  H20,  showing 
two  atoms  of  hydrogen  to  one  of  oxygen  per  molecule : 
likewise  sulphuric  acid  has  the  formula,  H2S04;  sugar, 
C1oH,2011.  Sometimes  a  certain  group  or  combination  of 
symbols  will  be  contained  more  than  once  in  the  com- 
pound ;  in  such  cases  the  group  is  usually  enclosed  in 
parentheses  and  the  number  of  times  it  is  contained  ex- 
pressed by  a  subfigure.  Thus,  aluminum  carbonate  is  A12 
(C03)3  in  which  the  group  C03  occurs  three  times.  It 
might  be  written  C309,  but  for  reasons  which  will  ap- 
pear later  the  method  first  given  is  usually  followed.  If 
it  is  desired  to  represent  more  than  a  molecule  of  a  sub- 
stance, the  proper  figure  is  placed  before  the  formula  as 
a  coefficient.  Thus,  5K2CO3  indicates  five  molecules  of 
potassium  carbonate  and  the  coefficient  multiplies  each 
symbol  in  the  formula.  That  is,  in  SK^COo  there  are  not 
only  ten  atoms  of  potassium,  but  five  of  carbon  and  fifteen 
of  oxygen.  Sal  soda  has  the  formula,  Na2C03 . 10H20. 
Written  thus  it  is  typical  of  the  method  used  for  all  hy- 
drates. The  number  of  molecules  of  water  entering  into 
the  compound  is  indicated  by  the  coefficient  of  the  water. 
Written  thus,  that  the  compound  is  a  hydrate,  is  indicated 


108  APPLIED    CHEMISTRY 

at  once,  as  is  also  the  fact  that  the  combination  is  some- 
what of  a  molecular  or  loose  one. 

4.  Structural  Formulas. — Often  it  is  very  desirable 
to  show  how  the  atoms  are  arranged  in  the  molecule. 
Especially  is  this  true  in  the  case  of  many  compounds  of 
carbon,  in  which  two  or  more  may  have  the  same  per- 
centage  composition   and   same   molecular   weight,   but 
very  different  properties.     Thus,  C2H60  is  the  empirical 
formula  for  more  than  one  compound  in  which  there  are 
two  atoms  of  carbon,  six  of  hydrogen  and  one  of  oxygen 
per  molecule,  but  the  formula  shows  nothing  more.     Ob- 
viously, if  written  C2H5OH  or   (CH3)2O,  the  molecular 
weights  are  the  same,  but  the  first  indicates  an  alcohol 
and  the  second  an  ether.     To  the  chemist,  written  thus, 
they  indicate  the  manner  of  arrangement  of  the  atoms  in 
the  molecule.    This  is  shown  more  fully  thus ; 

H  H 

H-C-C-0-H,  ethyl  alcohol. 
H  H 

H      H 

H-C-0-C-H,  methyl  ether. 
H      H 

Such  formulas  as  these  are  called  structural  or  some- 
times graphic,  and  in  very  complex  compounds  are  of 
the  greatest  help  in  understanding  the  relations  existing. 

5.  Radicals. — In  many  compounds  certain  groups  of 
elements  will  be  found,  which  behave  as  if  they  were 
single  elements.     Thus  in  sulphuric  acid  and  in  all  the 
sulphates  there  occurs  the  group,  -  S04.    This  constitutes 
the  negative  portion  of  the  compound  and  in  case   of 
electrolysis  appears  at  the  positive  electrode.     It  can- 


SYMBOLS    AND   FORMULAS  109 

not  be  separated  out  or  isolated,  and  in  the  electrolytic 
apparatus  it  immediately  combines  with  the  anode  if 
that  be  possible;  if  not,  it  combines  with  hydrogen  from 
the  water  present  and  forms  a  molecule  of  sulphuric 
acid.  Looking  at  the  formulas,  K2S04,  CuS04, 
A12(S04)3,  K2A1,(S04)4,  we  see  the  same  combination  of 
elements.  All  such  groups  are  called  radicals.  Ordi- 
narily the  term  indicates  a  group  of  atoms  forming  a 
part  of  a  compound  but  unable  to  exist  alone.  There 
is  only  one  common  electropositive  radical,  ammonium, 
NII4  - ;  it  is  found  in  all  ammonium  compounds.  Thus  am- 
monium chloride,  NH4C1,  ammonium  sulphate  (NH4)2S04. 
The  other  more  common  radicals  are  -  N03  seen  in  nitric 
acid  and  all  nitrates,  -  C03  in  the  carbonates,  -  P04  in 
phosphates,  -  C103  in  chlorates,  -  HO  in  hydroxides. 

6.  Equations. — Chemical  changes  or  reactions  have 
been  classified  as  being  mainly  of  three  kinds.  It  is 
customary  among  chemists  to  show  what  takes  place 
in  a  chemical  change  by  an  equation.  The  left  hand  side 
contains  the  formulas  of  the  substances  used  and  the 
right  hand  side,  the  products  formed,  with  the  sign  — > 
between,  which  is  read  yields  or  produces.  Going  back 
to  the  experiment  of  heating  mercuric  oxide,  we  find  that, 

Mercuric  oxide,  heated,  yields  oxygen  and  mercury. 
For  the  sake  of  brevity  this  is  written, 

HgO  (heated)  ->  Hg  +  0 
or  better, 

2HgO(heated)   -*  2TTg  +  02. 

It  was  stated  in  the  preceding  chapter  that  the  oxygen 
molecule  contains  two  atoms.  It  is  known  that  all  sub- 
stances exist  as  aggregations  of  molecules  and  not  of 
atoms.  The  second  equation  just  above  shows  the  oxy- 


110  APPLIED    CHEMISTRY 

gen  in  the  molecular  form  as  it  would  exist  after  'it  has 
been  liberated  from  the  compound,  hence  is  the  better 
form. 

Again,  water  electrolyzed,  gives  hydrogen,  two  parts 
and  oxygen,  one.  More  briefly,  but  indicating  the  same 
thing, 

2H20  ->  2H2  +  02 

Equations  are  not  something  merely  abstract  as  equations 
in  algebra,  or  merely  theoretical.  Every  equation  must  be 
verified  by  actual  experiment,  otherwise  it  has  no  value. 
For  example,  we  prepared  hydrogen  by  allowing  sodium 
to  react  with  water.  Algebraically  we  might  write  the 
equation, 

2Na  +  H20-»Na20  +  H2  or 
2Na  +  2H20  -*  2NaHO  +  H2. 

Only  by  experiment  can  we  know  which  is  correct.  The 
first  of  the  two  equations  shows  sodium  oxide  formed ; 
the  second,  sodium  hydroxide.  Which  is  correct  ?  Chem- 
ical tests  show  that,  performed  as  the  experiment  was, 
sodium  hydroxide  is  present;  hence,  the  equation  must 
be  written  to  show  that  fact.  We  prepared  oxygen  by 
heating  potassium  chlorate,  KC103.  Theoretically,  all  or 
part  of  the  oxygen  might  be  displaced  by  heating  the  com- 
pound, just  as  was  the  case  when  sodium  reacted,  as 
above,  with  water  in  producing  hydrogen.  Testing  the 
residue  shows  that  potassium  chloride  is  present,  and  our 
equation  must  be  written  to  indicate  the  fact,  thus, 

2KC103  ->  2KC1  +  302. 

In  like  manner  all  equations  are  determined  by  experi- 
ment and  merely  state  in  brief  form  what  was  learned 
thereby. 


SYMBOLS    AND    FORMULAS  111 

Exercises  for  Review 

1.  What  was  the  origin  of  symbols?     Give  the  purpose  of  a  sym- 
bol now. 

2.  Define  a  symbol. 

3.  Of  what  do  symbols  consist  and  how  written?     Illustrate. 

4.  Give  several  derived  from  the  Latin  or  Greek. 

5.  What  is  a  formula   and  what  does  it   represent   in  its  broad- 
est sense? 

6.  What   effect  has  a  coefficient  before   a  formula?     Illustrate. 
How  is  it  different  from  the  coefficient  as  used  in  algebra? 

7.  What  is  a  structural  formula?     Of  what  advantage? 

8.  What  is  a  radical?     Give  five.     How  are  they  different  from 
compounds? 

9.  What  is  the  purpose  of  an  equation?     What  do  they  show? 

10.  Which  is  the  better  form,  and  why :     2K  +  2H2O  -»  H2  +  2KHO, 
or,  K  +  II2O  ->  H  +  KHO? 

11.  How  do  chemists  know  whether  an  equation  is  correct? 

12.  Is  this  equation  true:  CiiSO4  +  2KHO  -»  Cu(HO)2  +  K2SO4? 
How  can  you  find  out? 


CHAPTER  VIII 

SOME  CHEMICAL  PROBLEMS 

Outline- 
Practical  Value  of  the  Equation 

Problems  in  Manufacturing  Industries 
Percentage  Composition  of  Compounds 
Problems  in  Combustion 
Liter  Weights  of  Gases 
Determination  of  Formulas 

1.  Value  of  Equations, — Almost  every  manufacturing 
industry  involves  more  or  less  chemistry.  In  baking 
powders,  of  the  three  ingredients  most  often  used,  two 
of  them  must  be  exactly  proportioned,  otherwise  the 
food  in  which  they  are  used  will  be  valueless.  The 
chemical  change  occurring  when  such  chemicals  are  put 
together  is  first  determined  by  experiment  in  the  labora- 
tory; this  is  then  expressed  by  an  equation,  and  from 
this  without  repeating  the  experiment  the  quantities 
needed  may  be  calculated  by  any  one  at  any  time.  To 
illustrate  with  a  case  somewhat  simpler  than  that  of 
baking  powder,  we  have  learned  that 

2KC103  -»  2KC1  +  302. 

This  equation  shows  that  two  molecular  weights  of  po- 
tassium chlorate  produce  three  molecular  weights  of 
oxygen.  Calculating  these  weights  from  the  table  of 
atomic  weights  given  on  p.  441,  we  find  that  245  parts  of 
potassium  chlorate  yield  96  of  oxygen.  Suppose  a  man- 
ufacturer needs  to  know  how  much  oxygen  he  can  obtain 
from  1,000  grams  of  potassium  chlorate.  Knowing  from 

112 


SOME    CHEMICAL   PROBLEMS  113 

the  equation  that  245  grams  of  the  chlorate  will 
produce  96  of  oxygen  1,000  will  produce  x  grams,  or 

245  :  96  :  :  1,000  :  x, 

from  which  x  may  be  easily  calculated.  Or,  putting  it  in 
another  form,  the  oxygen  obtained  is  seen  to  be  96/245 
of  the  weight  of  the  chlorate  used.  The  oxygen  obtained, 
therefore,  would  be 

96/245  of  1,000  ^96X1>°QQ 
245 

Manufacturers  of  oxygen  for  use  in  the  oxyhydrogeii 
blowpipe  or  for  other  purposes  furnish  it  in  gaseous  form, 
which  might  sometimes  be  given  in  volume  and  not 
weight  as  above.  Knowing  the  weight  of  a  liter  of  oxy- 
gen, 1.43  gram,  which  may  be  obtained  by  multiplying 
the  weight  of  a  liter  of  hydrogen  by  the  density  of  oxy- 
gen, if  we  divide  the  weight  obtained  above  by  the  weight 
of  a  liter  of  oxygen  we  shall  have  the  volume.  It  may  also 
be  obtained  another  way,  which  is  often  easier.  It  has 
already  been  stated  that  a  gram  molecular  weight  of  oxy- 
gen as  of  any  other  gas  is  22.4  liters.  By  looking  at  the 
equation, 

2KC103  ->2KC1  +  302, 

we  see  that  two  molecular  weights  of  potassium  chlorate 
produce  three  molecular  weights  of  oxygen.  But  3  gram 
molecular  weights  of  oxygen  would  be,  in  volume,  three 
times  22.4  liters.  That  is,  245  grams  of  potassium  chlo- 
rate would  produce  3  x  22.4  liters  of  oxygen,  or  67.2 
liters.  Hence,  1,000  grams  of  potassium  chlorate  would 
yield 


Tli  is  would  be  the  volume  under  standard  conditions  of 


114  APPLIED    CHEMISTRY 

temperature  and  pressure.  If  the  gas  is  to  be  delivered 
under  five  atmospheres'  pressure,  according  to  Boyle's 
law,  five  volumes  of  the  uncompressed  gas  must  be  pre- 
pared for  every  one  of  that  to  be  delivered. 

2.  To  Find  Percentage   Composition. — Knowing   the 
formula,  the  method  is  very  simple.     Suppose  it  is  de- 
sired to  know  the  amount  of  water  contained  in  Epsom 
salt,    MgS04.7H20.      Ascertaining    the   atomic   weights 
from  the  table,  p.  441,  we  have 

24 +  32 +  64 +(7x18)  =246. 

The  weight  of  the  seven  molecules  of  water  is  126.  It  is, 
therefore,  126/246  of  the  whole  compound,  or  51.2  per 
cent. 

3.  Some  Combustion  Problems. — Ordinary  combustion 
has  been  defined  as  rapid  oxidation.     It  is  often  desir- 
able to  know  the  character  and  quantity  of  products 
formed  as  well  as  the  amount  of  air  needed  for  per- 
fect combustion.     Natural  gas  consists  mainly  of  what 
is  known  as  marsh  gas,  CH4.    When  it  burns  the  follow- 
ing equation  illustrates  the  change  taking  place, 

CH4  +  202->C02  +  2H20. 

This  shows  that  one  volume  of  marsh  gas  requires  two 
volumes  of  oxygen  and  produces  one  of  carbon  dioxide 
and  two  of  vapor.  Applying  Avogadro's  hypothesis, 
any  problems  involving  volumes  may  be  read  off  at  once 
from  the  equation.  Suppose  1,000  cubic  feet  of  marsh 
gas  are  burned;  from  the  equation  we  can  see  that  twice 
as  much  oxygen  would  be  needed  and  there  would  be 
produced  the  same  volume  of  carbon  dioxide  and  twice 
the  volume  of  water  vapor.  As  air  is  only  about  one- 
fifth  oxygen,  to  burn  this  volume  of  gas  would  require 


SOME    CHEMICAL   PROBLEMS  115 

10,000  cubic  feet  of  air.  Acetylene  is  a  gas  producing 
great  heat  when  properly  burned  and  often  used  in  blow 
pipe  work  for  welding, 

2C2H2  +  502  ->  4C02  +  2H20. 

The  equation  indicates  that  two  volumes  of  acetylene  re- 
quire five  of  oxygen  and  yield  four  of  carbon  dioxide 
and  two  of  vapor.  From  this  it  is  seen  at  once  that  1,000 
cubic  feet  of  the  gas  would  need  two  and  a  half  times 
as  much  oxygen  or  2,500  cubic  feet,  and  would  produce 
2,000  cubic  feet  of  carbon  dioxide  and  1,000  of  vapor. 
When  rooms  are  warmed  by  an  open  gas  heater  or  by  an 
oil  stove,  by  which  the  necessary  oxygen  is  taken  directly 
from  the  room  and  the  products  left  in  the  room,  it  is 
seen  how  rapidly  the  air  is  being  vitiated.  The  water  pro- 
duced in  such  cases  is  often  sufficient  to  loosen  the  paper 
upon  the  walls,  and  even  the  parts  of  furniture  glued 
together.  It  must  be  remembered  that  the  air  being  used 
is  more  than  five  times  the  volume  of  the  oxygen  shown 
in  the  equation. 

4.  To  Find  the  Weight  of  a  Liter  of  Any  Gas.— It  is 
not  necessary  for  the  student  to  commit  to  memory  many 
figures.  But  the  weight  of  a  liter  of  hydrogen  should 
be  remembered,  for  by  means  of  it  the  weight  of  a 
liter  of  other  gases  may  readily  be  calculated.  It  is  nec- 
essary first  to  determine  the  vapor  density  of  the  gas, 
that  is,  its  density  compared  to  hydrogen.  Obviously, 
from  Avogadro's  hypothesis,  if  we  divide  the  molecular 
weight  of  any  gas  by  the  molecular  weight  of  hydrogen, 
we  shall  have  the  density  of  the  gas  compared  to  hydro- 
gen. The  molecular  weight  of  hydrogen  is  2,  hence  divid- 
ing the  molecular  weight  of  any  gas  by  2  gives  its  vapor 
density.  Then,  knowing  the  weight  of  a  liter  of  hydrogen, 
if  we  multiply  this  by  the  density  we  shall  have  the 


116  APPLIED    CHEMISTRY 

weight  of  a  liter  of  the  gas  in  question.  To  illustrate: 
Take  carbon  dioxide,  C02.  It  has  a  molecular  weight  of 
44 ;  its  vapor  density  would,  therefore,  be  22 :  multiply- 
ing the  weight  of  a  liter  of  hydrogen,  .0898,  by  22  gives 
1.9756  as  the  weight  of  a  liter  of  carbon  dioxide. 

5.  Determination  of  Formulas. — Knowing  by  experi- 
ment the  percentage  composition  of  a  substance,  and 
the  atomic  weights  of  the  elements  contained,  it  is  possi- 
ble to  determine  the  empirical  formula.  Thus,  wood  al- 
cohol contains  31l/2  per  cent  of  carbon,  12%  per  cent 
of  hydrogen  and  50  per  cent  of  oxygen.  Dividing 
these  percentages  by  the  atomic  weight  of  each  element, 
on  the  assumption  that  they  are  microcriths  of  weight 
and  not  percentages,  we  have 

37'5     =3.125          ^==12.5  4?- ==3.125. 


12  1  16 

Had  the  figures  representing  per  cents  really  been  mi- 
crocriths, as  assumed,  the  quotients  would  have  been 
the  number  of  atoms  of  each  element  in  the  formula. 
While  the  assumption  is  not  true,  the  mathematical  re- 
lation obtained  is  true,  that  is,  for  every  3.125  atomic 
weights  of  carbon  there  would  be  12.5  atomic  weights 
of  hydrogen  and  3.125  of  oxygen.  If  we  divide  through 
by  the  smallest  of  these  weights  we  shall  remove  the 
fractional  amounts  and  obtain  as  a  result,  carbon,  1; 
hydrogen,  4  and  oxygen,  1.  The  formula,  therefore, 
would  be  CH40.  To  know  whether  this  is  correct  the 
vapor  density  of  the  alcohol  must  be  determined.  Sup- 
pose by  experiment  this  is  found  to  be  16.  We  know 
from  a  previous  statement  that  the  molecular  weight 
is  double  the  density,  hence  the  molecular  weight  of 
this  compound  would  be  32.  By  adding  the  atomic 
weights  represented  in  the  formula  obtained,  CH40, 


SOME    CHEMICAL    PROBLEMS  117 

we  obtain  32,  which  agrees  with  the  weight  obtained  by 
experiment ;  hence  is  correct.  Take  another  case.  Anal- 
ysis of  sulphuric  acid  shows  it  to  contain  hydrogen, 
2.04  per  cent;  sulphur,  32.65;  oxygen,  65.30.  Dividing 
these  figures  by  the  respective  atomic  weights  we  have  as 
the  quotients,  2.04,  1.02  and  4.08,  which  give  the  relative 
number  of  atomic  weights  contained  in  the  molecule. 
Dividing  \)y  the  smallest  quotient,  we  have  as  a  result, 
2,  1,  4  respectively,  giving  for  the  formula  H.,S04.  Again, 
acetylene  has  a  percentage  composition  of  carbon,  92.31, 
and  hydrogen,  7.69  per  cent.  Dividing  by  the  atomic 
weights  we  have  as  the  quotients,  7.7  and  7.69.  Dividing 
these  results  \)y  7.69  we  have  1  and  1  respectively,  which 
gives  as  the  empirical  formula  for  acetylene,  GIL  Is 
this  correct?  By  experiment  in  the  laboratory  a  liter 
of  acetylene  is  found  to  weight  1.167  grams.  As  a  liter  of 
hydrogen  weighs  .0898  grams,  acetylene  is  found  to  be 
thirteen  times  as  heavy.  The  molecular  weight,  therefore, 
must  be  2  x  13,  or  26.  If  CII  were  the  formula,  its  molec- 
ular weight  would  be  only  13 ;  hence,  the  empirical  for- 
mula we  obtained  by  calculation  is  just  half  the  correct 
one ;  in  other  words,  it  must  be  doubled,  so  that  it  becomes. 
C2H2. 

Exercises  for  Review 

1.  Determine  the  weight   of  oxygen  obtainable  from  980  grams 
of  potassium  chlorate.     What  volume  would  the  oxygen  have? 

2.  How  much  potassium  chlorate  would  be  needed  to  prepare  500 
liters  of  oxygen  if  under  five  atmospheres'  pressure? 

3.  What   weight   of  hydrogen  may  be   had   from   260    grams   of 
zinc  by  allowing  it  to  react  with  sulphuric  acid?     Suppose  hydro- 
chloric acid  were  used,  what  would  be  the  weight  of  hydrogen? 

4.  What  weight  of  sulphuric  acid  would  be  needed  to  react  with 
100,  grams  of  magnesium  in  preparing  hydrogen?     What  would  be 
the  volume  of  the  hydrogen  obtained? 

5.  Calculate  the  per  cent  of  sulphur  in  sulphuric  acid.     Also  the 
per  cent  of  oxygen. 


118  APPLIED    CHEMISTRY 

6.  What     is     the    percentage    of    water    in    sal    soda;    formula, 
Na2C0310H20? 

7.  The  gas  ethylene  has  the  formula,  C2H4.     If  1,000  liters  of 
it   are  burned,  what   volume  of  carbon   dioxide  is  produced  and 
what  of  water  vapor? 

8.  Find  the  weight  of  a  liter  of  oxygen;    of  carbon  monoxide, 
CO;  of  ozone;  of  nitrogen  monoxide,  N2O;  of  arsenic  vapor. 

9.  The  percentage  composition  of  a  certain  alcohol  is  carbon, 
52.17,    hydrogen,    13.04,    and    oxygen    34.78.      Find   the    empirical 
formula. 

10.  If  the  vapor   density   of   nitric   oxide   is   15,   is  its   formula 
NO  or  N2O2? 


CHAPTER  IX 

THE  HALOGENS 
Outline — 

Relation  of  the  Halogens  to  Each  Other 
Chlorine,  its  History 

(a)   Preparation  in  Laboratory 
(ft)   Commercial  Methods 

(c)  Physical  Characteristics 

(d)  Chemical  Characteristics 

(e)  Uses 
Hydrogen  Chloride 

Characteristics 
Hydrochloric  Acid 

(a)   Preparation 

(6)   Characteristics 

(c)   Uses 
Hydrofluoric  Acid 

Uses 
Bromine 

(a)   Occurrence 

(&)  Preparation 

(c)  Characteristics 

(d)  Uses 
Iodine 

(a)   Occurrence 
(6)   Preparation 

(c)  Characteristics 

(d)  Uses 

1.  General  View. — There  are  four  elements  in  the  halo- 
gen group — fluorine,  chlorine,  bromine  and  iodine.  They 
are  called  halogens,  a  word  meaning  salt  producers,  be- 
cause they  all  produce  many  compounds  resembling  com- 
mon salt;  and  from  the  similarity  of  their  physical  char- 
acteristics and  their  chemical  behavior,  must  be  re- 
garded as  belonging  to  a  single  group  of  elements.  Their 

119 


120  APPLIED    CHEMISTRY 

densities  compared  to  hydrogen  are  in  the  order  given 
above,  with  atomic  weights,  respectively  of,  approxi- 
mately, 19,  35.5,  80  and  127.  Their  chemical  activity 
is  in  the  inverse  order  of  their  densities,  that  of  iodine 
being  the  least.  All  have  an  irritating  odor,  although 
that  of  iodine  is  rather  feeble  when  compared  with  the 
others.  The  two  lightest  are  gases;  bromine  is  a  liquid, 
the  only  liquid  element  except  mercury,  and  iodine  is 
a  solid. 

2.  Discovery  of  Chlorine.— It  will  be  remembered  that 
in  1773  Scheele  prepared  oxygen  by  heating  manganese 
dioxide  with  sulphuric  acid.  The  following  year  he  ob- 
tained chlorine  by  treating  manganese  dioxide  with 
hydrochloric  acid,  although  he  had  no  idea  he  had  dis- 
covered a  new  element.  Knowing  that  it  was  possible 
to  obtain  oxygen  from  manganese  dioxide,  he  believed 
he  had  simply  caused  a  union  between  the  hydrochloric 
acid  and  the  oxygen  of  the  dioxide.  And,  in  accordance 
with  the  phlogistic  ideas  of  combustion,  he  named  the 
gas  dephlogisticated  marine  acid  air.  At  that  time  oxy- 
gen was  often  called  dephlogisticated  air;  hence,  the 
name  in  modern  chemical  terms  would  be  oxidized  hydro- 
chloric acid  gas,  for  marine  acid  was  then  what  we  now 
call  hydrochloric.  More  than  a  quarter  of  a  century 
passed  away  and  chlorine  was  still  unknown  as  an  element 
until  Sir  Humphrey  Davy  gave  it  a  careful  study  and 
so  pronounced  it. 

3.  Preparation  of  Chlorine.— The  usual  laboratory 
method  of  preparing  chlorine  is  the  same  as  used  by 
Scheele.  (Fig.  27.)  The  accompanying  figure  shows  one 
form  of  apparatus  and  the  method  of  collecting.  Being  a 
gas  much  heavier  than  air  it  may  be  collected  by  downward 
displacement.  As  it  is  considerably  soluble  in  water,  the 
plan  used  in  the  case  of  hydrogen  and  oxygen  is  not  satis- 


THE    HALOGENS 


121 


factory,  but  may  be  employed  if  the  water  has  a  consid- 
erable amount  of  common  salt  dissolved  in  it.  The  man- 
ganese dioxide  is  placed  in  the  flask,  and  when  the  col- 
lecting bottles  are  all  ready  the  hydrochloric  acid  is  added 
through  the  thistle  tube  and  gentle  heat  applied  as 
needed. 

4.  Commercial  Methods. — As  chlorine  is  used  so  ex- 
tensively in  various  ways,  several  processes  of  obtaining 
it  cheaply  have  been  devised.  Since  common  salt  is 


Fig.   27. — Preparation   of  chlorine   in  the   laboratory. 

abundant  and  not  expensive,  one  of  the  plans  widely 
adopted  is  that  of  separating  its  constituents,  sodium 
and  chlorine,  by  electrolysis.  There  are  many  difficul- 
ties in  the  way  of  carrying  out  the  method  successfully, 
but  one  type  of  machine  is  shown  in  Fig.  28.  In  the  cen- 
ter compartment  the  bundle  of  carbon  rods  serves  as 
the  cathode,  while  a  heavy  carbon  rod  enters  each  of 
the  two  outer  compartments,  giving  a  double  anode. 
The  cathode  dips  into  pure  water,  the  anodes  into  sat- 


122 


APPLIED    CHEMISTRY 


urated  salt  solution;  a  thin  layer  of  mercury  covers  the 
bottom  of  the  apparatus  and  fills  two  grooves  into 
which  the  partitions  dip,  shown  by  the  heavily  shaded 
portion  in  the  figure.  Chlorine  being  an  electronegative 
element  is  liberated  at  the  anodes  and  is  drawn  off, 
dried,  and  compressed  in  tanks  or  drums.  The  sodium, 
electropositive,  is  repelled  by  the  anodes,  moves  toward 
the  cathode,  meets  the  mercury  and  is  dissolved  by  it. 
In  the  figure,  E  is  an  eccentric  which  rocks  the  tank 
continually.  In  this  way  the  mercury  containing  the 
sodium  is  brought  into  contact  with  the  water,  where- 


0E  FA 

Fig.   28. — Manufacture    of    chlorine. 

upon  the  sodium  reacts  with  the  water  forming  sodium 
hydroxide.     The  two  reactions  are 

2NaCl  ->  C12  +  2Na, 
2Na  +  2H20  ->  H2  +  2NaHO. 

5.  Physical  Characteristics  of  Chlorine. — Chlorine  is 
a  .greenish-yellow  gas,  about  two  and  a  half  times  as 
heavy  as  air,  and  of  very  irritating  odor.  It  may  be 
liquefied  at  —  33.6°  C.  at  atmospheric  pressure  and  in 
this  condition  is  a  limpid,  golden  yellow  fluid.  It  may 
be  kept  thus  sealed  hermetically  in  strong  glass  tubes. 
At  about  -102°  C.  it  becomes  a  pale  yellow  solid,  which 
upon  further  cooling  changes  to  a  pure  white  substance 
resembling  snow.  Upon  melting  it  assumes  the  same 


THE    HALOGENS  123 

yellow  color  again.     It  is  soluble  in  water  about  two 
volumes  to  one. 

6.  Chemical  Characteristics. — Chlorine  is  an  exceed- 
ingly active  element,  possibly  even  more  so  than  oxygen. 
Nearly  all  the  metals,  especially  in  a  finely  divided  form 
or  in  thin  sheets,  ignite  spontaneously  in  chlorine.  So- 
dium must  be  heated  before  combustion  takes  place, 
but  when  this  is  done  the  action  is  vigorous  with  the 
formation  of  common  salt.  Turpentine,  near  its  boil- 
ing point,  on  a  strip  of  blotting  paper,  when  lowered  into 
.a  jar  of  chlorine,  catches  fire  almost  instantly,  produc- 
ing an  immense  quantity  of  black  smoke.  Yellow  phos- 
phorus in  a  deflagrating  spoon  in  chlorine  begins  to  burn 
almost  immediately,  and  a  jet  of  hydrogen,  lighted  in 
the  air,  continues  to  burn  as  well  or  better  than  before. 
From  these  experiments  it  is  evident  that  combustion 
means  more  than  the  union  of  a  substance  with  oxygen. 
Any  two  substances,  combining  with  such  rapidity  as  to 
produce  heat  and  light,  undergo  combustion.  Chlorine 
attacks  the  throat  and  bronchial  tubes,  causing  great 
suffering  for  which  there  is  no  good  antidote.  A  satu- 
rated solution  of  chlorine  in  water,  if  surrounded  by  ice, 
deposits  yellow  crystals  of  chlorine  hydrate,  having  the 
composition  C1.4H20.  A  mixture  of  equal  parts  of  hy- 
drogen and  chlorine,  if  exposed  to  bright  sunlight,  ex- 
plodes with  violence.  The  light  from  a  burning  magne- 
sium ribbon  will  bring  about  the  same  results.  A  solu- 
tion of  chlorine  in  water,  exposed  to  strong  light,  decom- 
poses, forming  hydrochloric  acid  and  setting  free  the  oxy- 
gen. This  is  shown  by  a  simple  experiment  illustrated  by 
Fig.  29.  The  test  tube  is  filled  with  chlorine  water  and 
inverted  over  an  evaporating  dish  partly  filled  with  the 
same  solution.  In  a  short  time,  bubbles  of  gas  may  be 
seen  rising  to  the  top  of  the  tube;  when  the  action  has 


124  APPLIED    CHEMISTRY 

ceased  the  color  will  all  have  disappeared  from  the  water. 
Chemical  tests  show  that  the  gas  is  oxygen  and  that  at 
the  close  the  water  contains  hydrochloric  acid.  The  final 
result  is  shown  by  the  equation, 

2H20  +  2C12  -»  O2  +  4HCL 

7.  Uses  of  Chlorine. — Chlorine  is  used  extensively  for 
bleaching,  especially  cottons  and  linens.  The  cloth  is 
drawn  slowly  through  successive  vats  of  bleaching  pow- 
der solution  and  dilute  hydrochloric  acid.  Thus  the 
chlorine  is  set  free  and  oxidizes  the  coloring  matter. 
Much  of  the  paper  pulp  used  is  bleached  in  the  same 
way,  and  in  the  Middle  West  most  of  the  large  flour 


Fig.  29. — Effect  of  sunlight  on  chlorine  water. 

mills  employ  liquid  chlorine  to  bleach  their  products, 
to  enable  them  to  compete  with  other  flours  which  by 
nature  need  no  such  bleaching.  Practically  all  steam 
laundries  now  use  chlorine  to  whiten  the  cotton  and  linen 
goods  in  order  to  please  a  critical  public.  Such  frequent 
use  of  chlorine  upon  the  fibers  of  the  cloth  greatly 
weakens  them  and  hastens  the  end  of  their  usefulness. 
Chlorine  is  frequently  employed  as  a  disinfectant;  its 
use  for  the  destruction  of  pathologic  germs  in  city  wa- 
ters has  already  been  mentioned.  Bleaching  powder, 
a  compound  formed  by  the  interaction  of  chlorine  with 
lime  is  valuable  in  the  sick-room;  a  small  amount  in  a 


THE   HALOGENS  125 

saucer,  moistened  with  water,  slowly  gives  off  chlorine 
to  the  air.  The  quantity  is  so  small  as  to  be  unnoticea- 
ble  except  close  at  hand,  yet  by  diffusion  throughout 
the  room  brings  very  valuable  results.  Chlorine  is  also 
used  in  the  extraction  of  gold  from  its  ores :  for  this 
purpose,  bleaching  powder,  treated  with  hydrochloric 
acid  is  frequently  employed,  but  in  places  remote  from 
railway  or  other  good  means  of  transportation  liquid 
chlorine  put  up  in  steel  cylinders  is  used.  Chlorine 
was  the  first  of  the  poisonous  gases  used  in  the  late  war. 
Steel  cylinders  filled  with  the  gas  liquefied  by  great 
pressure  were  opened  with  nozzles  towards  the  Allies 
with  the  wind  blowing  in  that  direction.  Carried  down 
hill  by  its  own  weight  and  aided  by  the  wind  the  huge 
greenish-yellow  billows  caused  the  greatest  suffering 
and  thousands  of  deaths.  Later  the  gas  mask  was  de- 
vised to  protect  the  wearer  against  such  attacks.  In 
the  American  mask  all  the  air  taken  into  the  lungs  was 
compelled  to  pass  through  a  specially  absorptive  kind  of 
charcoal  made  from  the  shells  of  nuts,  or  of  charcoal 
mixed  with  an  antichlor,  a  substance  which  combines  with 
the  chlorine.  One  of  the  best  substances  of  this  nature 
is  what  is  known  by  photographers  under  the  name  of 
hypo  or  sodium  thiosulphate. 

8.  Hydrogen    Chloride. — This     compound    has    been 
known  to   chemists   several  hundred   years,   under   the 
names,   spirit   of  salt   and  marine   acid  air.     It  was   so 
named  because  prepared  from  common  salt,  at  that  time 
derived  mostly  from  the  Mediterranean  Sea. 

9.  Physical  Characteristics  of  Hydrogen  Chloride. — It 
is  a  colorless  gas  of  very  irritating  odor,  and  considera- 
bly heavier  than  air.     It  is  very  soluble  in  water ;  a  liter 
of  water  at  0°  C.  will  absorb  between  500  and  600  liters 


126  APPLIED    CHEMISTRY 

of  the  gas.  In  other  words,  600  liters  are  about  the 
same  as  600  quarts  or  three  50-gallon  barrels,  so  that 
one  quart  of  ice  water  will  absorb  about  three  barrels  of 
hydrogen  chloride.  Blowing  across  the  top  of  a  tube  or 
flask  in  which  the  gas  is  being  evolved  always  shows 
heavy  white  fumes ;  this  is  because  the  moisture  of  the 
breath  is  absorbed  and  condensed  by  the  gas.  When  a 
jet  of  hydrogen  burns  in  a  bottle  of  damp  chlorine,  or 
turpentine  upon  the  blotting  paper  as  previously  de- 
scribed, a  white  cloud  always  appears,  from  the  condensa- 
tion of  the  moisture  by  the  hydrogen  chloride  formed. 

H2  +  C12  ->  2HC1 

C10H16  +  8C12->16HC1  +  10C. 

These  two  equations  represent  the  burning  of  hydrogen 
and  of  turpentine  respectively  in  an  atmosphere  of  chlo- 
rine. A  liter  of  the  hydrogen  chloride  weighs  1.64  grams. 
At  -83.7°  C.  it  becomes  a  colorless  liquid  and  at  -110° 
a  solid.  The  liquid  has  no  effect  upon  dry  metals  such 
as  zinc  and  others,  readily  acted  upon  by  the  solution  of 
the  gas. 

10.  Hydrochloric  Acid. — When  hydrogen  chloride  gas 
is  allowed  to  pass  into  water  the  solution  formed  is 
called  hydrochloric  acid.  The  ordinary  commercial  va- 
riety, yellow  in  color,  due  to  the  presence  of  small  quan- 
tities of  iron  chloride,  is  sold  under  the  name,  muriatic 
acid.  It  was  formerly  a  by-product  obtained  in  the  man- 
ufacture of  sodium  carbonate,  the  first  step  of  which  in- 
volves the  treatment  of  common  salt  with  sulphuric  acid. 
At  temperatures  such  as  those  obtained  in  the  laboratory 
with  the  bunsen  burner,  the  following  reaction  takes 
place, 

NaCl  +  H2S04  ->  HCl  +  NaHS04. 

In  the  factories  a  much  higher  temperature  is  used  with 


THE    HALOGENS  127 

double  the  quantity  of  salt  which  results  in  a  different 
reaction,  thus, 

2NaCl  +  H2S04  ->  2HCl  +  Na2S04. 

The  gas  thus  obtained  is  conducted  into  towers  filled  with 
coke  or  some  similar  material,  which  is  kept  moist  by  wa- 
ter trickling  over  it.  Owing  to  its  great  solubility  the 
gas  is  all  absorbed  and  when  concentrated  the  solution  is 
the  acid  of  commerce. 

11.  Characteristics     of     Hydrochloric     Acid. — When 
pure  it  is  a  colorless  solution.     If  a  weak  solution  be 
boiled  it  becomes  more  and  more  concentrated  until  it 
reaches  about  20  per  cent   of  hydrogen  chloride ;   one 
stronger  than  this,  if  heated,   gives  off  the   gas  faster 
than  the  water  until  it  reaches  a  strength  of  about  20 
per  cent,  when  it  remains  constant.     Ordinary  concen- 
trated hydrochloric  acid  contains  about  36  per  cent  of 
hydrogen  chloride  and  is  strongly  acid.     Litmus  paper 
is  turned  red  as  are  various  other  vegetable  colors  or 
dyes;   by   such   metals   as   magnesium,   iron,   zinc   it   is 
readily    decomposed   with   the    evolution    of   hydrogen. 
Thus, 

Zn  +  2HCl  ->  H2  +  ZnCl2, 
Mg  +  2HC1  ->  H2  +  MgCl2. 

This  is  very  different  from  the  action  of  the  liquid  hy- 
drogen chloride.  The  two  are  not  different  in  appearance, 
but  the  latter,  as  previously  stated,  does  not  affect  dry 
metals;  neither  is  it  a  conductor  of  electricity,  whereas 
the  acid  is. 

12.  Uses. — A  century   ago   hydrogen   chloride   was   a 
waste  product  of  the  Leblanc  process  of  making  soda 
crystals.     Being  heavier  than  air  it  settled  doAvn  from 
the  lofty  towers  built  to  carry  it  away,  destroying  veg- 
etable life  and  corroding  tools  and  everything  of  a  me- 


128  APPLIED    CHEMISTRY 

tallic  character.  When  conducted  into  streams  it  killed 
the  fish  and  other  aquatic  animals,  so  that  eventually 
most  stringent  laws  were  enacted  against  all  such  manu- 
facturers. Finally,  by  the  aid  of  chemical  research, 
valuable  uses  were  suggested  for  it,  and  now  it  ranks 
among  the  most  valuable  of  the  acids.  Every  laboratory 
uses  it  abundantly;  almost  every  manufacturing  in- 
dustry employs  it  to  a  greater  or  less  extent.  In  the  stom- 
ach it  is  believed  to  be  an  essential  of  digestion.  The 
fact  that  bones,  very  imperfectly  masticated,  are  readily 
digested  by  various  carnivorous  animals  is  explained 
by  the  excessive  amount  of  hydrochloric  acid  found 
in  their  stomach,  which  dissolves  the  mineral  matter 
from  the  bones  and  leaves  them  about  as  soft  as  so 
much  gelatine.  Hydrochloric  acid  is  used  mixed  with 
nitric  acid,  three  parts  of  the  former  to  one  of  the 
latter,  in  what  is  called  aqua  regia.  The  words  mean 
royal  water  and  were  so  employed  for  the  reason  that 
formerly  this  was  the  only  known  solvent  for  gold,  the 
king  of  metals.  The  solution  is  effected  by  the  chlorine 
which  is  set  free  thus, 

3HC1  +  HN03  -»  2H20  +  2C1  +  NOC1. 

13.  Hydrofluoric  Acid. — The  preparation  of  hydrogen 
fluoride  is  similar  to  that  of  the  corresponding  com- 
pound of  chlorine.  The  cheapest  natural  compound  of 
fluorine  is  calcium  fluoride,  known  as  fluor  spar,  CaF2. 
This  is  mixed  with  sulphuric  acid  and  heated  in  a  plati- 
num retort.  A  colorless,  irritating  gas  distils  over, 
which  is  caught  in  water.  This  solution  is  the  hydro- 
fluoric acid  of  commerce.  It  is  put  on  the  market  usu- 
ally in  ceresine  or  wax  bottles.  At  ordinary  tempera- 
tures the  gas  is  believed  to  have  the  formula  H2F2. 
Above  30°  C.  it  begins  to  decompose  and  at  a  little  be- 


THE    HALOGENS  129 

low  90°  the  density  of  the  vapor  indicates  a  molecular 
weight  of  20  which  is  that  for  the  formula  HP.  Its 
chief  use  is  for  etching  glass.  The  article  to  be  etched 
is  covered  with  paraffin,  the  design  is  cut  in  the  wax  so 
as  to  expose  the  glass,  and  the  hydrofluoric  acid  is 
dropped  on.  In  a  very  few  minutes  the  etching  is  done. 
Graduations  upon  scientific  instruments  and  apparatus 
such  as  barometers,  burettes,  pipettes  and  the  like,  are 
thus  made.  The  following  equations  show  the  chemical 
reactions  in  preparing  the  hydrogen  fluoride  and  the 
glass  etching, 

CaF2  +  H2S04  -*  H2F2  +  CaS04, 
CaSi03  Na2Si03  +  6H2F2  ->  2NaF  +  CaF2  +  2SiF4  +  6H20. 

The  silicon  fluoride  is  a  gas  and  escapes,  while  the  cal- 
cium and  sodium  fluorides  are  solids  which  are  washed 
away  in  cleaning  the  glass.  Porcelain  and  chinaware, 
in  being  prepared  for  hand  decoration,  are  often  treated 
with  hydrofluoric  acid  to  remove  the  glazed  surface  and 
thus  cause  the  gold  or  other  decoration  to  adhere  the 
better. 

Bromine 

14.  Where  Found. — Bromine  in  potassium  and  mag- 
nesium bromide  occurs  in  nature  associated  with  com- 
mon  salt.     Being   more   soluble   than   salt,   these   com- 
pounds do  not  crystallize  out  as  readily;   hence,  they 
are  usually  found  in  the  upper  layers  of  salt  beds.     Our 
supply  is  largely  obtained  as  a  by-product  of  the  salt 
works  of  Ohio,  Kentucky  and  Michigan. 

15.  Preparation. — The  method  is  very  similar  to  that 
for  the  preparation  of  chlorine.     It  will  be  remembered 
that   in   the   laboratory   chlorine   is   made    by   treating 
manganese  dioxide  with  hydrochloric  acid.     Hydrobro- 


130  APPLIED    CHEMISTRY 

mic  acid  is  not  an  article  of  commerce,  because  of  its 
instability;  hence,  it  must  be  prepared  as  needed.  If 
magnesium  bromide  or  any  other  bromide  is  treated 
with  sulphuric  acid,  hydrogen  bromide  may  be  obtained, 
thus, 

MgBr2  +  H2S04  ->  2HBr  +  MgS04. 

It  has  many  properties  similar  to  hydrogen  chloride  in 
that  it  is  a  colorless  gas,  has  a  very  irritating  odor,  and 
is  very  soluble  in  water.  For  the  last  reason  it  con- 
denses moisture  in  the  air  or  from  the  breath  readily. 
Passed  into  distilled  water,  hydrobromic  acid  is  formed, 
but  it  very  soon  begins  to  decompose  and  in  a  few  days 
no  acid  at  all  remains.  In  preparing  bromine,  if  man- 
ganese dioxide  is  added  to  the  mixture  of  magnesium 
bromide  and  sulphuric  acid,  we  have  conditions  similar 
to  those  in  the  preparation  of  chlorine.  First  the  hy- 
drogen bromide  is  formed,  then  this  oxidized  by  the 
manganese  dioxide  with  the  formation  of  free  bromine. 
It  is  then  distilled  out  and  condensed  under  water.  The 
following  equation  shows  the  final  reaction, 

MgBr2  +  Mn02  +  2H2S04  -»  MgS04  +  MnS04  +  2H20  +  Br, 

16.  Physical  Characteristics. — Bromine  is  a  dark  red- 
dish-brown liquid,  the  only  liquid  nonmetallic  element. 
It  is  a  little  more  than  three  times  as  heavy  as  water  in 
which  it  is  not  greatly  soluble — about  3  c.c.  in  one  hun- 
dred.    It  is  a  very  volatile  liquid ;  hence,  if  a  bottle  of 
it  is  left  open  it  soon  passes  off  into  the  air.     It  boils 
at  59°  C.  and  solidifies  at  -  7.3,  in  slender,  needle-like 
crystals.     Its  vapors  are  exceedingly  irritating  to  the 
throat  and  bronchi,  and  upon  the  skin  the  liquid  pro- 
duces serious  and  painful  burns;  therefore,  the  utmost 
care  must  be  exercised  in  handling  it. 

17.  Chemical  Characteristics. — Many  of  the  character- 
istics of  chlorine  are  observable  in  bromine,  but  in  a 


THE    HALOGENS  131 

less  marked  degree.  A  jet  of  hydrogen  burns  in  a  bot- 
tle of  bromine  vapor  producing  white  fumes  due  to  the 
hydrogen  bromide  formed.  A  mixture  of  the  two  gases, 
however,  is  not  explosive,  but  a  platinum  sponge  greatly 
hastens  the  union  as  was  the  case  with  the  chlorine  and 
hydrogen  mixture.  A  piece  of  yellow  phosphorus,  placed 
in  bromine  vapor,  does  not  usually  ignite,  but  a  slow 
combination  takes  place,  with  the  formation  of  phos- 
phorous tribromide.  If  a  small  drop  of  liquid  bromine 
be  allowed  to  fall  upon  a  piece  of  yellow  phosphorus, 
the  action  is  immediate.  The  chemical  union  is  so  vi- 
olent that  the  phosphorus  is  ignited,  bursts  into  frag- 
ments, and  burns  vigorously.  Small  pieces  of  antimony 
dropped  upon  bromine  in  a  test  tube  become  red-hot 
almost  instantly,  float  around  upon  the  liquid,  and  fin- 
ally disappear.  The  chemical  reaction  is 

2Sb  +  3Br2  -*  2SbBi%. 

With  many  other  metals  the  action  is  equally  violent. 

18.  Uses. — Bromine  is  used  to  some  extent  in  the  lab- 
oratory  in   analytical   work,   but   more   largely   in   the 
manufacture  of  aniline  dyes.    The  compounds,  potassium 
and  magnesium  bromide,  are  used  in  medicine,  mainly  as 
sedatives. 

Iodine 

19.  Occurrence. — Like   chlorine    and   bromine,    iodine 
in  the  form  of  compounds  occurs  in  sea  water.     From 
this  it  is  separated  by  certain  seaweeds,  especially  kelp, 
and  stored  up  in  the  form  of  rather  complicated  com- 
pounds.    In  many  places  along  the  Pacific  Coast,  nota- 
bly, in  the  neighborhood  of  San  Diego,  vast  quantities 
of  kelp  are  found,  so  that  ocean  vessels  are  unable  to 
make  their  way  through.     In  the  form  of  compounds, 
sodium  iodide  and  iodate,  iodine  occurs  in  the  saltpeter 


132  APPLIED    CHEMISTRY 

beds  of  Chile  as  bromine  does  in  the  salt  beds  of  the 
United  States. 

20.  Preparation. — Formerly  most  of  the  iodine  of 
commerce  was  obtained  from  seaweeds.  They  were  cau- 
tiously burned  so  as  not  to  vaporize  the  iodine  present, 
and  the  ashes  were  treated  as  in  the  preparation  of  bro- 
mine, that  is  with  manganese  dioxide  and  sulphuric 
acid.  The  equation  is  similar  : 

2KI  +  3H2S04  +  Mn02  ->  MnS04  +  2KHS04  +  2H20  + 12 

The  iodine  distils  out  and  is  condensed.    It  is  purified  by 
vaporizing  again  in  specially  constructed  furnaces,  shown 


Fig.    30. — Apparatus   for   purifying  iodine    by   sublimation. 

in  Fig.  30.  In  recent  years  probably  more  of  the  iodine 
supply  has  come  from  the  deposits  in  Chile;  although 
during  the  late  war  in  the  manufacture  of  potassium 
and  other  compounds  from  kelp  much  iodine  'was  ob- 
tained as  a  by-product. 

21.  Physical  Characteristics. — Iodine  is  a  lustrous,, 
nearly  black  solid.  It  crystallizes  in  thin  plates,  which 
even  at  room  temperature  are  volatile,  as  may  be  seen 
if  the  crystals  are  placed  in  a  white  dish.  Upon  warm- 
ing gently  it  vaporizes  without  melting.  The  process  is 
called  sublimation  and  is  used  for  purifying  iodine  and 


THE    HALOGENS  133 

other  substances  which  pass  directly  from  the  solid  to  the 
gaseous  condition  upon  heating.  It  corresponds  to  the 
distillation  of  liquids.  For  medical  purposes  iodine  is 
sublimed  more  than  once  as  is  indicated  by  the  labels 
upon  the  bottles  marked,  resublimed.  Iodine  has  an  odor 
resembling  dilute  chlorine.  It  is  very  slightly  soluble  in 
water,  barely  sufficient  to  color  the  solution.  However,  in 
a  solution  of  potassium  iodide  in  water  iodine  is  very  solu- 
ble, giving  a  dark  brown  color.  The  same  is  true  of  al- 
cohol and  ether  solutions,  in  both  of  which  liquids  it  is 
very  soluble.  Carbon  disulphide  is  also  an  excellent  sol- 
vent and  gives  a  beautiful  violet  solution;  starch  muci- 
lage is  turned  deep  blue,  a  reaction  which  serves  as  the 
test  both  for  iodine  and  starch,  as  may  be  needed.  The 
quantity  of  iodine  should  be  small,  just  sufficient  to  give 
the  solution  a  pale  yellow  color ;  otherwise,  the  starch 
will  turn  so  dark  it  will  appear  black.  To  the  eye  weak 
solutions  of  iodine  appear  not  unlike  those  of  bromine. 
They  may  be  distinguished  by  adding  1  or  2  c.c.  of  carbon 
disulphide  to  the  solution  of  iodine  or  bromine  and  shak- 
ing well.  As  the  carbon  disulphide  is  a  much  better  sol- 
vent than  the  water,  the  bromine  or  iodine  will  be  col- 
lected in  the  small  quantity  of  the  heavy  carbon  disulphide 
at  the  bottom  of  the  test  tube.  The  bromine  will  give 
a  golden  brown  and  the  iodine  a  purple  color. 

22.  Chemical  Characteristics. — These  resemble  those 
of  chlorine,  but  are  much  feebler.  A  crystal  of  iodine 
laid  upon  a  thin  slice  of  phosphorus  reacts  vigorously 
so  that  the  phosphorus  catches  fire  and  burns,  while 
considerable  of  the  iodine  is  vaporized.  Iodine  is  read- 
ily displaced  from  soluble  compounds  by  both  chlorine 
and  bromine,  but  much  more  easily  by  the  former. 
Thus, 

2KI  +  Cl,  -*  2KC1  + 1, 


134  APPLIED    CHEMISTRY 

Even  a  single  bubble  of  chlorine  causes  a  brown  dis- 
coloration of  the  liquid.  A  very  interesting  fact  about 
iodine  is  its  behavior  at  high  temperatures.  In  a  pre- 
ceding section  in  this  chapter  the  atomic  weight  of  io- 
dine was  mentioned  as  about  127.  Its  molecular  wreight 
is  found  to  be  254,  which  shows  that  like  chlorine  and 
bromine  it  is  diatomic.  When  heated  above  700°  C.  the 
vapor  becomes  lighter  and  lighter,  much  more  so  than 
agrees  with  Charles'  law,  until  at  1,700°  it  is  just  half 
what  it  was  at  700.  This  indicates  that  the  molecules 
have  been  broken  into  two  parts  and  that  the  gas  is  now 
monatomic.  The  same  is  true  of  bromine  vapor,  but  to 
a  considerably  less  extent.  It  must  be  noted  further 
that  as  the  temperature  is  lowered  the  lighter  molecules 
recombine  to  form  the  diatomic  molecules;  at  the  same 
time  a  very  considerable  amount  of  heat  is  evolved,  just 
as  when  steam  is  cooled  it  gives  off  the  heat  previously 
consumed  in  producing  it.  The  following  equation  il- 
lustrates what  is  happening, 

I2  *±  21. 

The  double  arrow  sign  used  is  read,  gives  reversMy. 
Such  changes  are  called  dissociation,  a  term  which  means 
the  process  of  decomposing  a  substance  and  reforming 
it  under  varying  conditions.  It  is  probable  that  at  all 
temperatures,  between  700  and  1700,  the  action  is  pro- 
ceeding in  both  directions,  that  is,  some  of  the  diatomic 
molecules  are  being  decomposed  and  others  are  being  re- 
formed by  the  union  of  two  monatomics. 

23'.  Uses. — Iodine  is  used  mainly  in  medicinal  prepa- 
rations. The  tincture,  the  best  known,  an  alcoholic  so- 
lution, is  used  as  a  counter-irritant  in  sprains,  bruises 
and  swellings;  as  a  germicide  in  preventing  the  spread 
of  erysipelas  and  other  similar  diseases ;  as  an  antiseptic 
in  surgical  operations  and  wounds  in  place  of  hydrogen 


THE    HALOGENS  135 

peroxide.  It  is  more  powerful,  more  penetrating  and 
more  lasting,  than  the  peroxide,  but  at  the  same  time 
much  more  severe,  causes  much  more  irritation,  and  in 
unskilled  hands  is  much  less  safe.  lodoform,  CHI3,  is 
a  pale-yellow  solid;  has  a  peculiar  odor,  disagreeable  to 
most  individuals;  is  strongly  germicidal,  and  often  used 
by  physicians  as  an  antiseptic  in  contagious  diseases, 
lodothyrin,  an  extract  obtained  from  the  thyroid  gland 
of  sheep  is  sometimes  used  in  cases  of  underdevelop- 
ment  of  the  same  gland  in  the  human  body. 

Exercises  for  Review 

1.  Name  the  halogens  and  state  why  so  called. 

2.  Who   discovered  chlorine?  What  was  the   discoverer's   idea 
regarding  it?     What  was  the  old  name?     Who  proved  it  was  an 
element? 

3.  Give  usual  method  of  preparing  and  collecting  chlorine. 

4.  Describe  one  commercial  method  of  obtaining  chlorine. 

5.  Give  the  physical  characteristics  of  chlorine. 

6.  Give  the  chemical  characteristics. 

7.  Name  the  important  uses  of  chlorine. 

8.  How   is   hydrogen   chloride    prepared?      Give   its    character- 
istics. 

9.  How  is  hydrochloric  acid  prepared?     What  is  muriatic  acid? 

10.  Give  the  characteristics  of  hydrochloric  acid. 

11.  What  can  you  say  of  the  history  of  it?     Name  some  uses. 

12.  What  is  aqua  regia?     Why  so  called? 

13.  Give  the  uses  of  hydrofluoric  acid.   How  is  it  kept  for  use? 

14.  What  can  you  say  of  the  occurrence  of  bromine? 

15.  How  is  bromine  prepared  for  commerce?     Compare  method 
with  that  of  chlorine. 

16.  Describe  bromine.     What  danger  in  handling  it? 

17.  What  is  the  chief  use  of  bromine? 

18.  Where  is  iodine  found?     How  prepared? 

19.  Give  the  principal  characteristics  of  iodine — physical  and 
chemical. 

20.  What   is   sublimation?     How  is   it   different  from   distilla- 
tion? 

21.  Give  uses  of  iodine  and  iodine  compounds. 


CHAPTER  X 

ACIDS  AND  BASES 
Outline- 
Oxides,  Basic  and  Acidic 
Acids 
Bases 
.Nomenclature  of  Compounds 

(a)   Acids 

(6)  Bases 
Neutralization 
Salts 

(a)   Normal  or  Neutral 

(ft)   Acid 

(c)  Basic 

(d)  Nomenclature 

(e)  Binary 

1.  Oxides. — An  oxide  is  a  compound  consisting  of  only 
two  elements   one   of  which  is  oxygen.     Since   oxygen 
combines  with  all  the  elements  except  fluorine  and  the 
argon  group,  we  should  expect  there  would  be  a  very 
large  number.    Already  we  have  met  with  several.    Mer- 
curic oxide  has  been  used  in  preparing  oxygen ;  man- 
ganese dioxide  as  a  catalyst  in  making  oxygen  and  in 
the  preparation  of  chlorine,  bromine  and  iodine.    When- 
ever we  have  burned  a  metal  in  oxygen  or  the  air,  as 
for  example  iron  or  magnesium,  we  obtained  an  oxide. 
Likewise,  when  phosphorus  and  sulphur  were  burned  in 
oxygen  or  in  the  air  their  oxides  were  produced. 

2.  Two  Classes  of  Oxides. — If  oxides,  such  as  will  re- 
act with  water,  are  put  with  water,  some  will  be  found 
to  give  a  sour  taste,  and  will  turn  litmus  paper  red, 
while  others  thus  treated,  have  a  soapy  taste  and  turn 
reddened  litmus  paper  blue.     When  Lavoisier  gave  the 

136 


ACIDS    AND    BASES  137 

name,  oxygen,  meaning  acid  former  to  the  gas,  he  did  not 
recognize  the  fact  that  a  chemical  change  takes  place  be- 
tween certain  oxides  and  water,  but  considered  the  oxides 
themselves  as  acids.  Such  oxides  as  react  with  water  to 
form  acids  are  called  acidic  oxides,  or  anhydrides,  and 
those  that  form  hydroxides  with  the  water  are  called  basic 
oxides.  Typical  of  the  former  class  are  those  obtained 
when  sulphur  and  phosphorus  were  burned  in  oxygen. 
With  water  they  react  thus, 

S02  +  H2O  ^H2SO3, 
P2Q3  +  H20  ->  2HP03. 

The  most  familiar  basic  oxide  is  lime.  When  treated  with 
water  vigorous  chemical  action  results  accompanied  by 
great  heat.  The  equation  is 

CaO  +  H20  ->  Ca(HO)2 

Similar  reactions  are  those  of  sodium  and  potassium  ox- 
ides with  water, 

Na20  +  H20  -»  2NaHO,       ' 
K20  +  H20  -»  2KHO. 

A  careful  study  of  the  various  oxides  shows  that,  gener- 
ally speaking,  those  of  the  metals  react  with  water  more 
or  less  rapidly  to  produce  bases,  while  those  of  the  non- 
metalic  elements  are  anhydrides,  or  acid-forming  oxides. 
3.  Acids, — It  has  been  said  elsewhere  that  all  acids 
contain  hydrogen.  Most  of  them  also  contain  oxygen. 
If  all  were  formed  by  the  union  of  an  oxide  with  water, 
all  would  necessarily  contain  oxygen.  A  few,  such  as 
the  acids  of  the  halogens,  hydrofluoric  and  others,  are 
solutions  of  certain  compounds  and  are  not  formed  by 
the  interaction  of  some  oxide  with  water.  In  all  of 
them,  however,  the  hydrogen  forms  the  positive  part  of 
the  compound,  while  the  other  element  together  with 


138  APPLIED    CHEMISTRY 

the  oxygen  when  present,  constitutes  the  negative  part. 
It  is  the  hydrogen  in  a  peculiar  condition  which  will 
be  discussed  later  that  causes  all  acids  to  turn  litmus 
red. 

4.  Bases. — Theoretically,   at   least,   all  bases   may  be 
formed  by  the  interaction  of  a  metallic  oxide  and  water ; 
naturally  therefore,   all  must  contain  a   metal,   hydro- 
gen and  oxygen,  since  the  action  is  an  additive  one. 
They  are  all  called  hydroxides,  a  term  which  indicates 
that  they  contain  hydrogen  and  oxygen.     There  is  no  ex- 
ception to  this.    One  base  is  known,  however,  which  con- 
tains no  metal,  ammonium  hydroxide,  NH4HO,  but  the 
chemical  group,  NH4 — shows  many  of  the  characteristics 
of  a  metal.     The  soluble  bases  are  called  alkalies;  they 
are  potassium  hydroxide,  sodium  hydroxide,  ammonium 
hydroxide,  and  those  of  barium,  strontium  and  calcium. 
The  blue  litmus  test  which  they  give  is  due  to  the  hydroxyl 
group,  HO,  which  they  all  contain,  and  which  is  the  only 
thing  common  to  all. 

5.  Nomenclature. — Little  need  be  said  about  how  bases 
are   named.     They   are   all   called   hydroxides   with   the 
name  of  the  metal  prefixed,  thus:  Cu(HO)2  is  called  cop- 
per hydroxide  and  A1(HO)3  is  aluminum  hydroxide.    In 
a  preceding  chapter  the  gas,  HC1,  has  been  spoken  of  as 
hydrogen  chloride.    This  is  for  the  reason  that  when  per- 
fectly free  from  water  it  shows  no  acid  properties.    Like- 
wise,  we  should  expect  a   compound  with  the  formula 
H2S04  to  be  called  hydrogen  sulphate ;  H2C03,  hydrogen 
carbonate;  HNO3,  hydrogen  nitrate.     They  are  all  acids 
as  the  formulas  indicate  and  this  plan  would  be  in  accord- 
ance with  what  has  been  said  in  Chapter  I.     Attempts 
have  been  made  to  adopt  such  a  nomenclature,  but  as  sev- 
eral of  the  familiar  acids  were  discovered  and  in  common 
use  before  there  was  any  system  in  the  naming  of  com- 


ACIDS    AND    BASES  139 

pounds,  such  efforts  have  met  with  failure.  Accordingly, 
in  the  oxygen  acids  the  electronegative  element  suggests 
the  name.  Thus,  in  the  three  given  above,  sulphur,  car- 
bon and  nitrogen  have  given  the  respective  names.  This 
is  true,  generally.  However,  there  are  many  cases  in 
which  there  are  two  or  more  acids  formed  from  the  same 
three  elements.  Thus  sulphur  has 

H2S04  Sulphuric, 

H2S08  Sulphurous, 

H2S02  Hyposulphurous, 
and  chlorine  forms 

HC104  Perchloric, 

HC103  Chloric, 

HC102  Chlorous, 

HC10  Hypochlorous. 

In  such  case  the  quantity  of  the  oxygen  determines  the 
ending  of  the  name.  It  is  usually  true  that  the  most  com- 
mon acid  in  any  group  has  a  name  ending  in  ic;  then, 
the  one  with  a  smaller  amount  of  oxygen  next  to  this  is 
given  the  same  name  with  the  ending  changed  to  ous.  If 
there  be  others,  the  prefixes  hypo,  meaning  under,  and 
per,  meaning  beyond  or  above,  are  used.  This  is  seen  in 
the  four  chlorine  acids  given  above.  In  the  case  of  the 
acids  containing  no  oxygen  the  prefix  hydro  is  used  in 
all  cases,  thus, 

H2F2  Hydrofluoric, 

HC1  Hydrochloric, 

HBr  Hydrobromic, 

HI  Hydriodic 

H2S  Hydrosulphuric. 

6.  Neutralization. — If  a  base  and  an  acid  are 
brought  together  in  suitable  proportions,  chemical  ac- 
tion takes  place,  in  which  both  are  destroyed  and  new 


140  APPLIED    CHEMISTRY 

compounds  are  formed.  The  process  is  called  neutraliza- 
tion, for  the  reason  that  when  the  two  are  exactly  propor- 
tioned the  compound  resulting  affects  neither  red  nor 
blue  litmus  paper.  The  following  equations  illustrate 
a  few  cases, 

Ca(HO)2  +  H2S04  -»  CaS04  +  2H20, 

KHO  +  HC1  -^KC1  +  H20, 
Ba(HO)2  +  2HCl  ->  BaCl2  +  2H20, 

NaHO  +  HN03  -»  NaN03  +  H20, 
2NaHO  +  H2C03  ->  Na2C03  +  2H20. 

It  will  be  noticed  in  all  these  cases  that  one  of  the  pro- 
ducts is  water.  The  other  is  a  compound  which  is  not  a 
base  since  it  does  not  contain  hydroxyl;  it  is  not  an  acid 
since  it  has  no  positive  hydrogen.  It  is  a  new  compound. 
All  such,  produced  by  the  union  of  a  base  and  an  acid,  or 
by  a  similar  process,  are  called  salts.  This  name  was 
given  for  the  reason  that  a  very  large  number  of  them 
resemble  common  salt  and  may  be  formed  the  same  way. 
7.  Classes  of  Salts. — All  those  shown  in  the  equations 
just  above  are  called  neutral  or  normal  salts,  because 
the  hydrogen  has  all  been  removed  from  the  acid  and  the 
hydroxyl  from  the  base,  so  that  generally  speaking  they 
should  affect  neither  red  nor  blue  litmus.  However,  such 
proportions  of  the  acid  or  base  might  be  used  as  to  leave 
some  hydrogen  from  the  acid  or  some  hydroxyl  from  the 
base  not  thus  neutralized.  For  example, 

H2S04  +  NaHO  ->  NaHS04  +  H20, 

H3P04  +  NaHO  -»  NaH2P04  +  H20, 

H8P04  +  2NaHO  -»  Na2HP04  +  2H20, 

H3P04  +  3NaHO  -»  Na3P04  +  3H20. 

In  three  of  the  above  equations  some  of  the  hydrogen  re- 
mains in  the  salt  obtained  and  should  give  the  test.  In 
fact,  frequently  in  such  salts  the  sour  taste  of  the  acid  is 


ACIDS    AND   BASES  141 

still  very  noticeable  and  blue  litmus  is  quickly  reddened. 
All  such  are  called  acid  salts:  they  are  very  common. 
Obviously  such  an  acid  as  hydrochloric  could  not  form 
an  acid  salt.  It  must  be  observed  further,  that  not  all 
salts  containing  hydrogen  are  acid  salts.  Thus, 

NH4HO  +  HN03  -*  NH4N03  +  H2O, 
NaHO  +  HC2H302  -*  NaC2H302  +  H20. 

Both  the  salts  formed  in  these  equations  contain  hydro- 
gen, yet  both  are  neutral  salts.  In  both  cases  all  the 
positive  hydrogen  has  been  removed  from  the  acid.  In 
the  first  one,  the  hydrogen  remaining  in  the  salt  was  ob- 
tained from  the  base,  and  belongs  to  the  group,  NH4.  In 
the  second,  only  the  hydrogen  atom  written  by  itself  is 
positive:  the  other  three  are  combined  in  the  group 
C2H302  which  is  a  radical  and  the  hydrogen  is  not  free 
to  act  alone.  On  the  other  hand,  there  might  be  more 
hydroxyl  groups  present  in  the  base  used  than  the  hydro- 
gen in  the  acid  could  remove  in  the  formation  of  water. 
Thus, 

2Cu(HO)2  +  H2C03  -»  2H20  +  Cu2(HO)2CO3. 

Usually  this  is  written  CuC03.Cu(HO)2.  Such  salts 
are  not  as  common  as  the  acid  salts,  but  they  do  appear 
and  are  formed  in  various  ways.  They  are  called  basic 
salts.  The  above  is  called  basic  copper  carbonate. 

8.  Nomenclature  of  Salts. — The  common  salts  offer  no 
difficulties  to  the  student  in  their  nomenclature.     Thus, 

KBr  Potassium  bromide 

ZnCl2  Zinc  chloride 

K2S  Potassium  sulphide 

CuS04  Copper  sulphate 

NaN03  Sodium  nitrate 

CaC03  Calcium  carbonate, 


142  APPLIED    CHEMISTRY 

KC103  Potassium  chlorate, 

Na3P04  Sodium   phosphate, 

KI03  Potassium  iodate, 

KBr03  Potassium  bromate. 

Compounds  with  two  elements  have  names  ending  in 
ide;  while  the  others  end  in  ate  unless  formed  from  an 
acid  whose  ending  is  ous  when  the  salt  has  a  name  end- 
ing in  ite.  The  difficulty  is  with  the  compounds  formed 
from  the  same  three  elements  used  in  different  propor- 
tions. Thus, 
Na2S04  Sodium  sulphate,  formed  from  H2S04  sulphuric 

acid, 

Na2S03     Sodium  sulphite,  formed  from  H2S03  sulphur- 
ous acid, 
Na2S02     Sodium  hyposulphite,  formed  from  H2S02,  hy- 

posulphurous  acid, 
and 

KC104     Potassium  perchlorate  from  HC14  perchloric  acid, 
KC1O3     Potassium  chlorate  from  HC103  chloric  acid, 
KC102     Potassium  chlorite,   from   HC102   chlorous  acid, 
KC1O      Potassium   hypochlorite,    from   HC10    hypochlo- 

rous  acid. 

Only  memorizing  the  formulas  of  the  acids  in  the  series, 
and  the  fact  that  oxygen  acids  ending  in  ic  give  salts  end- 
ing in  ate;  and  ending  in  ous,  salts  ending  in  ite  can  suf- 
fice. However,  most  of  these  are  not  of  sufficient  import- 
ance in  warranting  the  beginner  in  making  the  attempt. 
Again,  the  acid  salts  offer  some  trouble,  thus, 

K2S04  is  potassium  sulphate, 

KHS04  is  acid  potassium  sulphate  or  potassium  hydro- 
gen sulphate.  As  there  can  be  only  one  acid  potassium 
sulphate  no  confusion  results  from  the  use  of  either  term. 


ACIDS    AND    BASES  143 

But  tribasic  acids,  like  phosphoric,  H3P04,  yield  two  acid 

salts,  thus, 

K3P04       Potassium  phosphate, 
K2HP04  Dipotassium  phosphate, 
KII2P04  Monopotassium  phosphate. 

As  the  last  two  are  both  acid  salts  they  could  not  be 
read  acid  potassium  phosphate,  for  either  might  be  meant. 
It  is  customary,  therefore,  to  follow  the  plan  suggested, 
in  which  the  amount  of  the  base  used  is  indicated  by  the 
prefix  di  or  mono.  The  fact  that  one  hydrogen  remains 
from  the  acid  in  the  salt  is  implied  by  the  prefix  di,  for 
the  reason  that  the  acid  originally  contained  three  hydro- 
gen atoms  and  only  two  have  been  replaced.  Likewise, 
mono  implies  that  two  atoms  of  hydrogen  remain  in  the 
salt. 

9.  Binary  Salts. — Compounds  of  two  elements  are 
called  binaries.  Such  are  all  salts  made  from  the  binary 
or  no-oxygen  acids.  Their  nomenclature  offers  no  diffi- 
culty except  in  cases  of  two  or  more  formed  from  the 
same  two  elements.  When  such  is  the  case,  the  endings, 
ous  and  ic  are  used  just  as  has  been  said  in  the  acid  end- 
ings. The  one  ending  in  ous  always  indicates  the  one 
full  of  or  having  the  greater  relative  amount  of  the  posi- 
tive part  of  the  compound.  Thus, 

Hg20  Mercurous  oxide, 

HgO  Mercuric  oxide, 

FeCl2  Ferrous  chloride, 

FeCl3  Ferric  Chloride, 

HgCl2  Mercuric  chloride, 

Hg2Cl2  Mercurous  chloride, 

Sn02  Stannic  oxide, 

SnO  Stannous  oxide. 

Oftentimes  prefixes  are  used  which  may  lessen  the  dif- 


144  APPLIED    CHEMISTRY 

ficulty.  Thus,  manganese  cfo'oxide  indicates  the  amount 
of  the  oxygen  ;  again  old  forms,  now  obsolete,  are  some- 
times used  which  are  often  obscure.  Thus,  Fe203  is 
sometimes  called  iron  sesquioxide,  instead  of  ferric  oxide. 
The  prefix  means  a  ratio  of  two  to  three  and  was  applied 
to  such  compounds  as  the  one  just  given.  Proto  and  sub, 
meaning  the  first  and  under  are  also  used  applied  to  the 
lowest  of  the  compounds  in  a  series. 

Exercises  for  Review 

1.  What  is  an  oxide?     Name  two  classes,  define  each  and  give 
examples. 

2.  What  can  you  give  for  the   composition   of  acids?     What 
two  tests  do  they  give? 

3.  Give   the   composition   of   bases?     What   tests   do   they   give? 

4.  What  is  an  alkali?    Name  five. 

5.  How  are  bases  named?    Acids? 

6.  Give   names   of   HC1O3,   HIO3,    HBr,   HBr03,   H2SO4,    H3PO4, 
Ba(HO),,  Ca(HO)2  NaHO. 

7.  What  is  meant  by  neutralization?     Write  an  equation  illus- 
trating. 

8.  Complete  the  following  equations: 


HCl  +  Ba(HO)2—», 
CaO  +  H2SO4  -^  , 


ZnO  +  H,SO4  ->  , 
Zn  +  H2SO4->. 

9.  How  many  salts  were  obtained  in  the  above  equations? 
Were  any  formed  without  the  use  of  a  base?  Why  was  this? 

.10.  What  is  a  salt?  Name  three  kinds.  Define  each  and  give 
examples. 

11.  Which    of   the    following   are    acid    salts:     KNO3,    KHSO4, 
CuSO4,  AgNO3,  K,HPO4,  KH2PO4,  K,PO4,  CaH2(CO3)2? 

12.  Give  names  of  all  formulas  in  question  11. 

13.  What  is  a  binary  compound?     Illustrate. 

14.  Give  names  of  FeO,  Fe,O3J  FeCl3,  Fe012,  CuS,  Cu2S,  H2O, 
H202,  Hg20,  HgO. 


CHAPTER  XI 

NITROGEN  AND  COMPOUNDS 
Outline — 

Nitrogen 

(a)   Occurrence 

(fc)   Preparation  from  the  Air 

(c)  Preparation  from  Chemicals 

(d)  Characteristics 
Ammonia 

(a)  Occurrence 

(b)  Commercial  Supply 

(c)  Uses 
Oxides  of  Nitrogen 

Nitric  Acid 

(tt)   Preparation 

(b)  Characteristics 

(c)  Uses 
Explosives 

(a)  'Gunpowder 
(6)   Nitroglycerine 
(c)   Dynamite 
(e?)   Nitrocellulose 

(e)  Smokeless  Powders 
(/)   Picrates 

(0)    T.N.T. 
Other  Products 

(a)  Collodion 

(b)  Celluloid 

(c)  Fiber  Silk 

1.  Occurrence  of  Nitrogen. — In  another  chapter  it  has 
been  seen  that  nitrogen  constitutes  about  four-fifths  of 
the  air.  It  is  found  in  many  compounds  in  nature,  es- 
pecially the  nitrates  of  sodium  and  potassium.  The 
former  occurs  in  large  quantities  in  Chile,  whence  it  is 

145 


146 


APPLIED   CHEMISTRY 


exported  to  all  parts  of  the  world.  Nitrogen  is  an  im- 
portant constituent  of  such  food  products  as  lean  meat, 
eggs,  beans  and  peas,  and  is  found  to  some  extent  in 
grains,  wood,  coals  and  like  substances.  Some  varieties 
of  coal  contain  in  the  neighborhood  of  2  per  cent. 

2.  Preparation. — By  removing  the  other  constituents 
of  the  air,  nitrogen  may  be  obtained  comparatively  pure 
except  for  the  admixture  of  the  argon.  This  is  generally 
done  by  the  use  of  phosphorus  or  by  passing  a  stream 
of  air  over  heated  copper  turnings.  The  proportion  of 
nitrogen  in  the  air  may  be  shown  somewhat  approxi- 


Fig.    31. — Method    of    determining    approximately    the    proportion    of    nitrogen 

in  the  air. 


mately  by  apparatus  shown  in  Fig.  31.  A  graduated 
cylinder  is  inverted  qver  a  deflagrating  spoon  with 
handle  bent  as  shown.  Into  the  spoon  is  put  a  piece  of 
yellow  phosphorus  the  size  of  a  small  bean;  then  the 
whole  is  placed  over  a  trough  of  water  and  the  cylinder 
clamped  so  that  the  water  level  inside  and  out  is  at  the 
zero  mark.  The  phosphorus  will  slowly  combine  with 
the  oxygen  and  at  the  end  of  two  or  three  days  the 
water  level  will  have  become  stationary  except  for  at- 
mospheric changes  of  pressure  and  temperature.  The 


NITROGEN    AND    COMPOUNDS  147 

volume  of  the  residual  nitrogen  and  argon  may  then 
be  read  off.  From  compounds  nitrogen  is  generally  pre- 
pared by  gently  heating  a  solution  of  ammonium  chlo- 
ride and  sodium  nitrite.  The  following  equations  illus- 
trate the  changes  taking  place, 

NH4Cl  +  NaN02  -»  NaCl  +  NH4N02, 
NH4N02  -»  N2  +  2H20. 

3.  Characteristics  of  Nitrogen. — Nitrogen  is  a  color- 
less gas,  slightly  lighter  than  air,  may  be  liquefied  at 
-194°  C.  and  solidified  at  -214°  C.    It  is  much  less  solu- 
ble in  water  than  oxygen.     Chemically,  it  is  a  very  in- 
active element;  it  will  not  burn  or  combine  with  many 
of  the  elements  directly.     Passed  over  strongly  heated 
magnesium  or  calcium  it  will  form  a  nitride  with  them. 
It  was  by  passing  nitrogen  over  heated  magnesium  that 
argon  was  discovered,   since  it  will  not  combine  with 
magnesium.       By    means    of    a    powerful    electric    dis- 
charge through  a  mixture  of  oxygen  and  nitrogen,  chem- 
ical union  takes  place  between  these  two  elements  with 
the  formation  of  one  or  more  oxides  of  nitrogen.    Like- 
wise a  mixture  of  hydrogen  and  nitrogen,  three  parts 
to  one,  by  means  of  the  electric  spark  is  slowly  changed 
into   ammonia.      The   uses   of   nitrogen   have   been   dis- 
cussed in  the  chapter  on  the  atmosphere. 

4.  Occurrence  of  Ammonia. — Because  of  the  fact  that 
certain  waste  products  of  the  animal  economy,  as  well 
as  other  nitrogenous  bodies  in  their  decomposition,  pro- 
duce ammonia  in  appreciable  quantities,  it  has  long  been 
familiar  to  scientists.     For  many  years  it  was  sold  in 
solution   under   the    name    "spirits    of   hartshorn"    be- 
cause of  the  fact  that  it  was  formerly  obtained  by  the 
distillation  of  the  horns  of  deer  and  cattle. 

5.  Commercial   Supply. — Some   varieties   of   ordinary 
soft  coal  contain  nitrogen  in  appreciable  quantities,  in 


148  APPLIED    CHEMISTRY 

the  form  of  compounds.  When  such  coals  are  heated 
the  nitrogenous  bodies  are  decomposed  and  the  nitrogen 
comes  off  as  ammonia,  NH3,  mixed  with  a  great  variety 
of  other  gases.  On  account  of  its  high  solubility  it  may 
be  largely  separated  from  the  others  by  passing  through 
towers  or  cylinders  containing  coke  or  something  simi- 
lar, kept  moist  by  dripping  water.  This  very  impure 
solution,  called  gas  liquor  is  drawn  off,  lime  is  added  and 
the  mixture  is  boiled.  The  ammonia  distils  out  and  is 
passed  into  either  hydrochloric  or  sulphuric  acid,  when 
the  chloride  or  sulphate  of  ammonia  is  formed, 

NH3  +  HC1  ->  NH4C1, 
2NH3  +  H2S04  -»   (NH4)2S04. 

By  treating  a  solution  of  either  of  these  salts  with  lime 
and  passing  the  gas  into  distilled  water,  pure  ammonium 
hydroxide  or  aqua  ammonia  is  obtained, 

(NH4)2S04  +  CaO--»  CaS04  +  2NH3  +  H20, 
NH3  +  H20  ->  NH4HO. 

6.  Characteristics  of  Ammonia. — Ammonia  is  a  color- 
less gas,  with  very  pungent  odor.    It  is  exceedingly  sol- 
uble in  water  so  that  about  1,200  liters  will  dissolve  in 
1  liter  of  water  at  0°  C.    Putting  it  into  other  words,  one 
quart  of  ice  water  will  absorb  nearly  six  barrels  of  am- 
monia gas.    It  may  be  liquefied  at  -38.5  C.  and  solidified 
at  -77°  C.    The  strong  ammonia  water  of  commerce  con- 
tains about  35  per  cent  of  the  gas  with  a  specific  gravity 
of  0.88.     At  ordinary  temperatures,  except  under  pres- 
sure, water  will  hold  only  about  28  per  cent  of  ammonia, 
and  at  100°  the  ammonia  is  entirely  expelled. 

7.  Uses  of  Ammonia. — Its  principal  use  is  in  the  liquid 
form  for  refrigeration  purposes.     From  a  container  the 
liquid  is  allowed  to  pass  through  a  needle  valve  into 
pipes  surrounded  by  a  solution  of  salt,  of  such  strength 


NITROGEN    AND    COMPOUNDS 


149 


that  its  freezing  point  is  much  lower  than  that  of  pure 
water.  A  pump  is  constantly  withdrawing  the  gasified 
ammonia,  thus  maintaining  a  partial  vacuum,  so  that 
a  rapid  evaporation  of  the  ammonia  is  secured.  The 
rapidity  of  the  evaporation  causes  a  lowering  of  the 
temperature  of  the  pipes  and  the  surrounding  brine, 
which  is  kept  circulating  by  a  special  brine  pump.  For 
cold  storage  purposes  this  brine  is  forced  through  pipes 
to  any  place  desired:  in  this  way  meats,  fruits,  but- 


Fig.   32. — Manufacture   of  ice. 

ter,  eggs,  and  all  other  perishable  food  products  may  be 
kept  near  the  freezing  point  for  long  periods.  For  pro- 
tection against  moths,  furs  and  woolen  clothing  are  often 
stored  thus  in  the  summer.  Temperatures  low  enough 
to  freeze  meats  may  easily  be  secured;  fishing  vessels, 
gone  on  long  trips,  often  return  after  months  with  their 
cargo  of  fish  frozen  solid.  Markets,  floral  shops,  and 
various  other  places  employ  these  methods  of  preserving 


150  APPLIED    CHEMISTRY 

their  goods;  everyone  has  seen  the  brine  pipes,  heavily 
coated  with  frost,  which  furnilsh  the  cold  for  such  pur- 
poses. For  the  manufacture  of  ice,  galvanized  iron 
boxes  filled  with  pure  water  are  lowered  into  the  brine 
tank.  In  from  sixty  to  seventy-two  hours  the  water  has 
become  solid,  whereupon  the  container  with  the  ice  is 
lifted  from  the  brine ;  a  stream  of  warm  water  is  run 
over  it  for  a  moment  to  loosen  the  ice,  when  it  slips  out 
and  slides  down  into  the  storage  room.  Fig.  32  shows 
the  main  steps  in  the  process.  When  the  ammonia  is 
withdrawn  from  the  pipes  it  is  again  compressed  and 
in  summer  time  is  cooled  by  streams  of  running  water, 
whereby  it  again  becomes  a  liquid.  It  is  said  that  to 
make  3  pounds  of  ice  requires  about  1  pound  of  ammo- 
nia, but  as  the  liquid  is  used  over  and  over  again  the 
process  is  very  cheap.  In  the  household,  ammonia  is  of- 
ten used  in  a  dilute  solution  for  softening  water  and  for 
similar  purposes.  In  commerce  it  finds  extensive  use  in  the 
manufacture  of  cooking  soda  and  of  sodium  carbonate. 
The  process  will  be  described  elsewhere  in  the  text. 

8.  The    Oxides. — There    are    five    oxides   of   nitrogen 
known.     They  are: 

Nitrous  oxide,  Nitrogen  monoxide,  N20, 

Nitric  oxide,  Nitrogen  dioxide,  NO,  sometimes  written 

NA, 

Nitrous  anhydride,  Nitrogen  trioxide,  N203, 
Nitrogen  peroxide,  Nitrogen  tetroxide,  N02,  also  writ- 
ten, N204, 
Nitric  anhydride,  Nitrogen  pentoxide,  N205. 

About  the  only  facts  of  interest  regarding  the  third  and 
fifth  in  the  series  are  that  they  are  the  anhydrides  of 
acids,  thus, 

N203  +  H20  ->  2HN02,  Nitrous  acid, 
N205  +  H20  -*  2HN03,  Nitric  acid. 


NITROGEN    AND    COMPOUNDS  151 

Nitric  oxide  is  mentioned  for  the  reason  that  almost  in- 
variably when  nitric  acid  is  added  to  a  metal,  it  is  pro- 
duced. However,  it  is  never  seen  unless  precautions  are 
taken  to  collect  it  over  water,  because  of  the  fact  that 
as  soon  as  exposed  to  the  air  it  combines  spontaneously 
with  oxygen  and  forms  the  tetroxide.  Thus, 

3Cu  +  8HN08  ->  2NO  +  4H20  +  3Cu(NOs)2; 

2NO  +  0,  ->  2X0,. 

The  peroxide  is  a  heavy,  reddish-brown  gas  resembling 
bromine  vapor,  with  very  irritating  odor.    It  is  very  sol- 
uble in  water  with  which  it  reacts,  thus, 
2N02  +  H20  ->  HN03  +  HN02. 

9.  Nitrous  Oxide. — Nitrous  oxide  may  be  prepared  by 
cautiously  heating  ammonium  nitrate,  thus, 

NH4N03  -^  N20  +  2H20. 

As  it  is  somewhat  soluble  in  cold  water  it  must  be  col- 
lected over  warm  water.  It  is  a  colorless  gas,  with  a  very 
faint  pleasant  odor.  In  it  various  substances  will  burn 
when  ignited  almost  as  well  as  in  oxygen  and  a  spark 
on  a  pine  splinter  will  burst  into  flame.  It  becomes 
a  liquid  at  about  -90°  C.  and  a  solid  at  -102°  C.  If  in- 
haled it  produces  insensibility  and  mixed  with  oxygen  it 
is  frequently  used  as  an  anesthetic  for  minor  surgical 
operations  such  as  the  extraction  of  teeth.  It  is  some- 
times called  laughing  gas,  because  of  its  intoxicating  ef- 
fects upon  some  individuals. 

10.  Nitric  Acid.— It  is  said  that  occasionally,  after  un- 
usually violent  electrical  storms  accompanied  by  little 
rain,  traces  of  nitric  acid  have  been  found  in  the  water 
which  has  fallen.    As  nitric  acid  is  an  oxyacid  it  should 
be  able  to  be  formed  in  this  manner. 

11.  Commercial  Preparation. — In  the  laboratory  and 
commercially  up   to   very  recent  times  nitric   acid  has 


152  APPLIED    CHEMISTRY 

always  been  prepared  by  treating  sodium  nitrate  with 
sulphuric  acid,  thus, 

NaN03  +  H2S04  ->  NaHS04  +  HN03. 

The  laboratory  form  of  apparatus  is  shown  in  the  illus- 
tration. No  corks,  either  rubber  or  otherwise,  may  be 
used  as  they  are  rapidly  attacked  by  the  fumes.  From 
the  fact  that  during  the  war,  trade  with  Chile  was 
largely  interrupted  so  that  adequate  supplies  of  sodium 
nitrate  could  not  be  obtained,  other  methods  had  to  be 
adopted.  Consequently,  preparation  from  the  air  dur- 
ing the  last  years  of  the  war  was  carried  on  extensively. 
At  points  where  electricity  of  high  voltage  could  be  ob- 


Fig.  33. — Preparation  of  nitric  acid. 

tained  cheaply  from  water  power,  by  electric  discharge 
through  a  slowly  moving  current  of  air,  certain  oxides 
of  nitrogen  are  obtained.  These  are  passed  into  water 
with  the  formation  of  nitrous  and  nitric  acid, 

H20  +  N203  ->  2HN02, 

2N02  +  H20  -»  HN02  +  HN03, 

N205  +  H20  ->  2HN03. 

As  nitrous  acid  readily  takes  up  more  oxygen  and  be- 
comes nitric,  the  ultimate  product  is  nitric.  It  is  prob- 


NITROGEN    AND    COMPOUNDS  153 

able  that  this  method  in  some  form  will  eventually  dis- 
place the  older  one  of  obtaining  nitric  acid  from  salt- 
peter. 

12.  Characteristics  of  Nitric  Acid. — When  pure,  ni- 
tric acid  is  a  colorless  liquid,  but  exposed  to  bright  sun- 
light,   or   heated,   decomposition   takes   place   with   the 
formation  of  sufficient  peroxide  to  color  the  liquid  more 
or  less  brown.    It  boils  at  86°  C.  and  solidifies  at  -47°  C. 
The  concentrated  acid  of  commerce  contains  68  per  cent 
nitric  acid,  with  a  specific  gravity  of  1.42.     Upon  the 
hands  or  clothing  it  produces  a  yellowish-brown  stain, 
which  cannot  be  removed  by  ammonia  as  can  those  of 
hydrochloric  acid.     It  is  a  strong  oxidizing  agent,  for 
reasons  shown  by  the  equation, 

2HN03  -»  H20  +  2N02  +  0. 

Prom  the  fact  that  it  thus  readily  yields  free  oxygen 
it  reacts  differently  with  metals  from  that  of  other  acids 
thus  far  mentioned.  Instead  of  giving  up  hydrogen  as 
do  hydrochloric  and  sulphuric,  when  put  with  a  metal, 
as  iron  or  zinc,  it  converts  the  metal  into  an  oxide. 
Then,  this  oxide  often  dissolves  in  other  portions  of  the 
acid  present  and  forms  a  nitrate.  For  example,  copper 
reacts  with  nitric  acid  forming  copper  nitrate,  Cu(N03)2 
and  nitric  oxide  and  water  but  no  hydrogen.  The 
changes  which  may  be  presumed  to  take  place  may  be 
represented  thus, 

3Cu  +  2HNO.,  -»  3CuO  +  H20  +  2NO, 
3CuO  +  6HN03  -*  3Cu(N03)2  +  3H20. 
Adding  the  two  equations  together  we  have  the  result 
as  obtained  by  the  actual  experiment, 

3Cu  +  8HN03  ->  3Cu(N03)  2  +  4H20  +  2NO. 

13.  Uses, — One  of  the  most  important  uses  of  nitric 
acid  is  in  the  manufacture  of  explosives.     Gunpowder, 


154  APPLIED    CHEMISTRY 

while  not  made  from  nitric  acid,  contains  potassium  or 
sodium  nitrate,  both  of  which  are  salts  of  nitric  acid. 
The  other  constituents  are  sulphur  and  charcoal,  but  the 
nitrate  forms  75  per  cent  of  the  whole.  Being  a  mix- 
ture, an  appreciable  length  of  time  is  required  for  the 
combustion  to  proceed  throughout  the  entire  mass; 
hence,  gunpowder  is  a  low  power  explosive.  Among 
those  of  high  power,  glyceryl  nitrate,  commonly  called 
nitroglycerine,  is  one  of  the  longest  known.  It  is  pre- 
pared by  treating  glycerine  with  fuming  nitric  acid. 
The  reaction, 

C3H5(HO)3  +  3HN03  -»  C3H5(.NOa)8  +  3H20, 

shows  that  for  every  molecular  weight  of  nitroglycerine 
produced  there  are  three  of  water  formed.  In  a  short 
time  this  would  so  dilute  the  nitric  acid  that  chemical 
action  would  cease,  or  become  exceedingly  slow.  It  be- 
comes necessary,  therefore,  to  remove  it.  This  is  done 
by  introducing  continuously  with  the  nitric  acid  fuming 
sulphuric,  which  as  we  have  seen  is  a  great  absorbent  of 
water.  In  this  way  the  process  becomes  continuous.  Ni- 
troglycerine is  a  heavy,  oily  liquid,  and  for  this  reason 
not  convenient  to  handle  or  transport.  Much  of  it  is 
therefore  made  into  dynamite  or  giant  powder  and  other 
explosives.  By  mixing  with  it  sawdust  or  kieselguhr, 
a  silicious  earth  of  tubular  structure,  both  of  which  have 
high  absorbtive  powers  for  nitroglycerine,  dynamite  is 
prepared.  It  is  commonly  sold  under  the  name  of  giant 
powder  with  percentages  of  nitroglycerine  ranging  from 
25  to  75.  It  is  used  in  the  form  of  sticks  or  in  coarse 
granules.  Such  explosives  as  these  are  fired  by  a  detona- 
tor, such  as  mercuric  fulminate,  Hg(CNO)2,  commonly 
called  fulminating  mercury.  This  compound  is  decom- 
posed by  a  sharp  blow,  giving  a  spark  and  heat  sufficient 


NITROGEN    AND    COMPOUNDS  155 

to  begin  the  decomposition  of  the  main  explosive.  All 
explosives  contain  combustible  material  and  within  them- 
selves oxygen  sufficient  or  nearly  so  to  burn  completely. 
In  two  nitroglycerine  molecules,  2C3H5(N03)3,  there  are 
6  atoms  of  carbon  and  10  of  hydrogen.  The  hydrogen 
requires  5  atomic  weights  of  oxygen  for  its  combustion 
and  the  carbon  12.  By  looking  at  the  formula  it  will 
be  seen  that  the  oxygen  is  a  little  more  than  sufficient,  as 
the  nitrogen  is  set  free  and  passes  off  in  this  condition. 
It  is  apparent,  therefore,  that  the  liquid  or  solid,  except- 
ing the  inert  material  used,  is  entirely  converted  into 
gases  of  very  great  volume,  which  through  the  heat  gen- 
erated are  enormously  expanded ;  coming  almost  instan- 
taneously the  pressures  are  tremendous  and  the  results 
terrific. 

14.  Nitrocellulose. — This  is  commonly  called  guncot- 
ton.  Cellulose,  of  which  filter  paper  or  cotton  is  largely 
composed,  has  the  formula,  (C6H10Or,)n-  Into  this  mole- 
cule we  may  introduce  nitrate  groups  as  in  the  case  of 
the  glycerine  and  by  the  same  method.  Water  is  a  by- 
product and  must  be  removed  as  before.  In  this  case 
any  number  of  nitrate  groups  may  be  substituted,  from 
three  to  six,  the  hexanitrate  being  much  more  explosive 
than  the  compounds  with  fewer  nitrate  groups.  The 
following  equation  shows  the  reaction, 

2CGH1(105  +  6HN03  ->  C12H1404(N03)0  +  6H20. 

The  products  of  the  explosion  are  the  same  as  before. 
Guncotton  is  safe  to  handle  if  kept  damp  and  in  this 
condition  it  is  uniformly  transported  on  shipboard  or 
elsewhere.  Even  when  damp  it  may  be  exploded  by  the 
use  of  a  detonator  or  electric  spark  with  a  small  amount 
of  dry  to  start  the  process.  It  is  used  in  mining  harbors 
or  other  places  against  attack  as  well  as  for  other  simi- 


156 


APPLIED    CHEMISTRY 


lar  purposes.  The  ternitrate,  being  much  less  explo- 
sive, when  dissolved  in  a  mixture  of  alcohol  and  ether, 
is  sold  under  the  name  collodion.  It  is  a  viscous,  quick- 
drying  liquid,  used  in  photography,  and  as  new  skin,  so- 
called,  in  medicine.  For  the  latter  purpose  a  small  per 
cent  of  Venice  turpentine  and  castor  oil  is  added  to  ren- 
der it  more  flexible  and  less  liable  to  crack  when  dried 
upon  the  skin.  If  a  solution  of  camphor  in  alcohol  is 
used  as  a  solvent  for  the  guncotton,  celluloid  is  obtained, 
the  uses  of  which  are  familiar.  Fiber  silk  is  another 
product  closely  related.  The  guncotton,  by  one  method, 
is  dissolved  as  in  making  collodion:  when  it  has  reached 


Fig.   34. — Some   forms   of   smokeless   powder. 

a  thick,  viscous  stage  it  is  forced  through  tiny  openings 
like  those  in  the  spinneret  of  the  spider  or  silk  worm. 
These  threads  dry  instantly  upon  coming  into  the  air, 
are  wound  on  bobbins  and  made  into  cloth  as  if  real  silk. 
The  explosive  nitrate  groups  must  be  removed  and  this  is 
done  by  treatment  with  an  alkali  or  with  calcium  sul- 
phide. The  luster  is  not  greatly  different  from  that  of 
real  silk,  but  the  fibers  are  more  brittle  and  the  wearing 
qualities  as  a  result  inferior. 

15.  Smokeless  Powders. — Two  varieties  are  sold  under 
the  names,  cordite  and  ~ballistite.    The  former  is  a  mixture 


NITROGEN   AND   COMPOUNDS  157 

of  nitroglycerine  and  guncotton  with  a  little  vaseline 
added.  Ballistite  is  a  mixture  of  the  same  two  ex- 
plosives to  which  is  added  a  small  amount  of  diphen- 
ylamine,  which  reduces  the  explosive  character.  Other 
varieties  are  simply  the  hexanitrate  cellulose  dissolved 
and  molded  into  various  shapes,  some  of  which  are 
shown  in  Fig.  34. 

16.  Picric  Acid  and  T.  N.  T. — Picric  acid  with  the 
formula,  CGH2(N02)3OH,  is  obtained  from  phenol,  com- 
monly known  as  carbolic  acid,  C0H5OII,  in  which  have 
been  substituted  three  nitro  groups  for  three  of  the  hy- 
drogen atoms.  This  will  be  seen  by  examining  the  two 
formulas.  It  is  a  very  explosive  substance  and  from  it  a 
very  considerable  number  of  high  explosives  have  been 
prepared.  An  intimate  mixture  of  red  lead,  Pb304,  with 
about  an  equal  volume  of  picric  acid  makes  a  powerful 
explosive  which  may  be  fired  by  heat  alone.  During  the 
war  a  great  deal  was  heard  about  the  explosive,  T.N.T. 
and  its  terrific  power.  Toluol  is  a  compound  closely  re- 
lated to  phenol,  with  the  formula,  CGH-CH3.  The  group, 
CH3,  has  taken  the  place  of  hydroxyl,  HO,  in  the  phenol. 
T.N.T.  is  trinitrotoluol,  with  the  formula,  CGH2(N02)3- 
CH3,  which  will  be  observed  is  toluol  with  three  hydrogen 
atoms  replaced  by  nitro  groups.  When  exploded  the  pro- 
ducts are  not  essentially  different  from  those  already  de- 
scribed elsewhere. 

Exercises  for  Review 

1.  State  where  nitrogen  occurs  in  nature.     What  food  products 
contain  it? 

2.  How  is  nitrogen  obtained  from  the  air?   How  from  chemicals? 

3.  Describe  nitrogen.     How  was  argon  discovered? 

4.  How  do  you  account  for  the  presence  of  ammonia  in  the  air? 

5.  What  is  spirits  of  hartshorn? 

6.  State   how   ammonia   is   prepared    for   commerce.      Write   the 
equations. 


158  APPLIED    CHEMISTRY 

7.  Describe  ammonia. 

8.  Give  important  uses  of  ammonia. 

9.  Name  the  oxides  of  nitrogen  and  give  formulas. 

10.  How  is  nitrous  oxide  prepared?     Chief  use? 

11.  How  is  nitric  acid  prepared?     Equation. 

12.  Explain  how  nitric  acid  is  made  synthetically.     What  led  to 
this? 

13.  Give  chief  properties  of  nitric  acid.     Why  is  it  an  oxidizing 
agent  ? 

14.  Give  important  uses  of  nitric  acid. 

15.  How  is  nitroglycerine  made?     Dynamite?     When  exploded, 
what  forms? 

16.  What  is  nitrocellulose?     Collodion?     Celluloid?     Fiber  silk? 

17.  Name  two  smokeless  powders.     State  how  made. 

18.  What  is  T.N.TJ 


CHAPTER  XII 

CARBON 

Outline — 

Occurrence  in  Nature 
Allotropic  Forms  of  Carbon 
Characteristics  of  Carbon 
Diamonds 

(a)   Origin 

(fc)   Uses 
Graphite,   Compared   with   the   Diamond 

Uses 
Coals,  How  Produced  in  Nature 

Varieties 
Petroleum 

(a)   Origin 

(&)   Kinds 

(c)   Products  obtained  by  Distillation 
Natural  Gas 
Charcoal 

(a)   Kinds 

(fe)  Uses 
Lampblack 
Coke 

Gas  Carbon 
Carbon  Monoxide 

(a)    Formation 

(&)   Characteristics 
Carbon  Dioxide 

(a)   Preparation 

(fc)   Characteristics 

(c)   Uses 
Other  Carbon  Compounds 

1.  Occurrence  of  Carbon. — The  relative  amount  of 
carbon  in  nature  is  not  large.  It  will  be  remembered 
that  it  is  not  among  the  eight  most  abundant  elements 

159 


160  APPLIED    CHEMISTRY 

which  constitute  almost  the  entire  amount  of  the  matter 
composing  the  earth.  However,  in  the  form  of  com- 
pounds it  is  familiar  in  a  very  great  variety.  In  fact, 
so  numerous  are  they  that  they  constitute  an  entirely 
separate  branch  of  chemistry,  called  organic,  for  the 
reason  that  years  ago  they  were  supposed  to  be  produced 
by  organized  or  life  forces  alone.  The  muscles  of  the 
body  consist  largely  of  proteins,  composed  mainly  of  car- 
bon, hydrogen,  oxygen  and  nitrogen.  The  stems  of  plants 
and  trunks  of  trees  are  largely  cellulose,  containing  car- 
bon, hydrogen  and  oxygen.  The  mineral  world  furnishes 
the  corals,  limestone,  marble,  calcite,  dog  tooth  spar,  and 
many  other  carbon  compounds.  It  is  some  form  of  car- 
bon that  constitutes  the  fuel  of  the  world ;  carbon  com- 
pounds in  the  form  of  starches,  sugars  and  fats  furnish 
heat  and  energy  for  the  human  body,  while  protein  foods, 
similar  compounds  of  carbon  containing  nitrogen,  are  nec- 
essary to  rebuild  the  wasted  muscles.  Carbon  thus  be- 
comes a  very  interesting  and  a  very  important  element. 

2.  Forms  of  Carbon. — The  only  pure  form  of  carbon 
is  the  diamond.    Graphite,  however,  although  in  appear- 
ance it  is  entirely  different,  is  nearly  pure ;  closely  re- 
lated are  anthracite  coal  and  the  artificial  forms,  coke, 
charcoal,   gas  carbon  and   lampblack.     Other   varieties 
of  coal  contain  less  free  carbon  and  more  bituminous 
compounds  of  carbon,  hydrogen  and  nitrogen.    Graphite 
may  be  considered  a  crystallized,  allotropic  form  of  the 
diamond,  and  lampblack  an  amorphous  or  uncrystallized 
allotrope. 

3.  Some  General  Characteristics. — The  physical  prop- 
erties of  carbon  are  so  entirely  different  in  the  three 
allotropic  forms   that   they  must   be    considered   sepa- 

/\ 

rately.  The  crystallized  varieties  will  burn  only  at  very 
high  temperatures  and  in  an  atmosphere  of  oxygen;  the 


CARBON  161 

amorphous  forms,  especially  the  more  impure,  burn 
readily  in  the  air  without  the  addition  of  great  heat. 
At  high  temperatures  carbon  combines  with  various 
elements  to  form  carbides.  It  is  a  strong  reducing  agent 
also  at  red  heat,  that  is  it  has  the  power  of  removing 
oxygen  from  its  combination  with  metals.  This  equa- 
tion will  illustrate, 

ZnO  +  C  -*  Zn  +  CO. 

4.  Proofs  for  Composition  of  Diamond. — If  heated  in 
the  absence  of  air  to  a  dull-red  temperature  the  diamond 
expands  considerably,  becomes  lighter,  and  turns  dark 
in  color.  If  put  into  a  tube,  as  shown  in  Fig.  35,  with 
the  air  replaced  by  oxygen,  and  heated  to  bright  red- 
ness, the  diamond  disappears  and  leaves  only  an  at- 


x-  -  diamond 

Fig,   35. — Burning   of   a   diamond. 

mosphere  of  carbon  dioxide.    A  piece  of  graphite  treated 
in  the  same  way  gives  like  results. 

5.  Origin  of  Diamonds. — Some  believe  that  diamonds 
are  of  meteoric  origin  and  not  native  to  the  earth,  but 
of  this  there  is  little  evidence.  Undoubtedly  they  were 
formed  under  great  pressure  and  a  temperature  suffi- 
ciently high  to  render  the  carbon  more  or  less  plas- 
tic, so  that  crystallization  took  place  upon  cooling.  The 
great  Kimberly  mines  of  South  Africa  have  been  thought 
to  be  the  crater  of  an  extinct  volcano,  and  some  mines 
discovered  in  other  places  seem  to  be  the  same.  The 
artificial  diamonds  made  by  Moissan  some  years  ago 
point  to  the  same  theory  as  probably  true.  lie  mixed 
fine  iron  filings  and  charcoal  made  from  sugar  together, 


162 


APPLIED    CHEMISTRY 


put  them  into  an  electric  furnace  made  from  a  block 
of  lime,  shown  in  Fig.  36,  and  by  the  electric  arc  melted 
the  iron.  It  is  well-known  that  molten  iron  will  dissolve 
small  amounts  of  carbon.  So  at  this  stage,  Moissan 
plunged  the  mass  into  cold  water,  whereupon  the  iron 
solidified  upon  the  outside,  and  by  its  contraction  pro- 
duced great  pressure  upon  the  interior.  Thus  the  dis- 
solved carbon  crystallized  under  sufficient  pressure  to 
give  it  the  density  of  the  diamond,  which  is  considerably 
above  that  of  graphite.  When  cool  the  mass  was  broken 
up  and  the  iron  dissolved  in  nitric  acid,  leaving  the 
diamonds  unaffected.  They  possessed  the  hardness  and 


Fig.   36. — Moissan's   electric   furnace. 

other  characteristics  of  native  diamonds,  but  were  dark 
in  color  due  to  the  presence  of  some  .uncrystallized  par- 
ticles of  carbon.  The  experiment  was  of  scientific  in- 
terest, because  of  the  fact  indicated  that  if  a  source  of 
heat  sufficient  to  melt  carbon  is  ever  found  artificial  dia- 
monds will  become  a  possibility. 

6.  Uses  of  Diamonds. — Until  it  was  discovered  that 
diamonds  could  be  cut  and  polished  by  their  own  dust, 
they  never  came  into  use  as  ornaments.  Imperfect  and 
discolored  diamonds  are  used  in  various  ways,  because 
of  their  hardness;  for  example,  in  the  bearings  of  fine 


CARBON  163 

watches,  delicate  balances,  for  cutting  glass,  polishing 
other  stones,  on  tips  of  drills,  and  other  similar  ways. 

7.  Graphite. — Next    to   the   diamond    graphite   is   the 
most  nearly  pure  form  of  carbon.     It  occurs  in  nature, 
but  not  in  sufficient  quantities  to  meet  the  demands  of 
commerce.    Compared  with  the  diamond  it  has  a  density 
of  only  2.3,  diamond  being  3.5 ;  it  is  a  good  conductor 
of  electricity,  the  diamond  poor;  graphite  occurs  in  six- 
sided  plates,  the  diamond  in  regular  octahedrons;  graph- 
ite is  a  soft,  greasy-feeling,  black  solid,  the  diamond  the 
hardest  mineral  known,  being  10  in  the  scale,  and  color- 
less.   Since  graphite  is  unaffected  by  the  air  it  is  used  to 
give  a  finished  coating  to  shot  and  the  grains  of  both 
black  and  giant  powder.     It  is  an  ingredient  of  most 
stove  polishes,  for  the  same  reason.     It  is  used  in  cru- 
cibles for  melting  very  refractory  substances  and  to  give 
conductivity    to    wax    plates    in    making    electrotypes. 
Mixed  with  oil  it  is  frequently  used  as  a  lubricant  for 
bearings  of  heavy  machinery.     The  most  familiar  of  its 
many  uses  is  in  the  so-called  ''lead  pencil."     This  con- 
sists of  a  mixture  of  graphite  and  clay,  proportioned 
in  such  a  way  as  to  give  varying  degrees  of  hardness 
from  very  soft  to  very  hard.     The  clay  and  graphite 
mixed  are  moistened  with  water,  made  into  a  soft  plia- 
ble mass  and  by  pressure  forced  through  small  openings 
in  metal  plates.     When  dried  these  "leads"  are  ready 
for  insertion  in  the  wooden  coverings  familiar   to  all. 

8.  Coals. — Natural  coals  are  believed  to  be  the  meta- 
morphosed remains  of  the  forests  of  another  day.    Grow- 
ing  at  a   time  possibly  when   there   was   more    carbon 
dioxide  in  the  air  than  now,  in  a  climate  warm  and  moist, 
the   forests   undoubtedly   surpassed   in   luxuriance   and 
density  anything  known  upon  the  earth  at  the  present 
day.     Swept  down  by  some  great  catastrophe  of  nature 


164  APPLIED    CHEMISTRY 

these  forests  were  buried  sufficiently  deep  to  protect 
them  from  decay  through  access  of  the  air  and  at  the  same 
time  to  subject  them  to  heat  and  pressure.  Under  vary- 
ing conditions  of  these  two  factors,  a  great  variety  of 
coals  was  formed,  ranging  from  lignite,  brown  in  color, 
soft,  and  often  showing  the  original  woody  structure, 
to  anthracite,  hard,  clean  and  lustrous.  Intermediate 
between  these  are  bituminous  coals  of  great  variety, 
rich  in  oily  products,  which  burn  with  a  yellow,  smoky 
flame,  and  semianthracite  with  most  of  the  bitumen  ex- 
pelled, which  burns  with  but  little  smoke  and  but 
slightly  yellow  flame.  Cannel  coal  is  very  rich  in  oily 
matter,  not  suitable  for  furnaces,  but  excellent  for  grate 
fires  on  account  of  the  freedom  with  which  it  burns  and 
the  abundant  yellow  flames  it  gives.  Peat  is  a  modern  va- 
riety of  coal  consisting  largely  of  roots  only  partly 
changed,  with  the  admixture  of  considerable  earthy  mat- 
ter. 

9.  Petroleum. — From  30  to  40  per  cent  of  some  coals 
is  an   oily   product.     This   may  be   easily   expelled   by 
heat.    Undoubtedly  anthracite  and  semianthracite  coals 
were  produced  by  the  greater  heat  to  which  they  have 
been  subjected,  which  resulted  in  the  volatilization  of 
the   oily  matter.     When  this  took  place   ages   ago,   if 
the  heat  was  not  so  great  as  to  decompose  the  bitumen 
in  the  soft  coal ;  it  was  expelled  and  found  its  way  into 
layers  of  sand  or  other  places  where  it  is  obtained  to- 
day as  rock  oil  or  petroleum.     Occasionally  it  is  under 
so  great  a  pressure  that  when  opened  up  it  shoots  far  above 
the  surface  in  a  "gusher. ' '    More  often  it  must  be  pumped 
from  the  well.    Fig  37  shows  a  number  of  oil  derricks 
with  the  customary  pumps. 

10.  By-products  of  Petroleum. — Petroleum  is  a  black 
or  brownish  oil  of  varying  density  and  viscosity,   com- 


CARBON  165 

posed  of  a  great  variety  of  carbon  compounds.  When 
dark  in  color  it  is  because  of  particles  of  free  carbon 
contained.  There  are  two  general  classes  of  these  oils: 
paraffin-base  and  asphalt -base.  These  names  are  given 
for  the  reason  that  in  the  former  the  thick,  less  volatile 
portion  of  the  oil  is  paraffin,  while  in  the  latter  it  is  as- 
phaltum.  The  paraffin  oils  are  regarded  as  the  more  de- 
sirable, for  the  reason  that  they  give  on  distillation  a 
higher  percentage  of  refined  products.  The  asphalt  oils 
are  regarded  by  some  as  of  animal  origin,  instead  of  veg- 


Fig.    37. — Oil    derricks,    a    familiar    sight    in    oil-producing    sections. 

etable,  but  produced  in  the  same  way.  When  petroleum 
is  heated  in  retorts,  the  low  boiling  oils  distill  over  first. 
The  process  is  spoken  of  as  fractional  distillation,  because 
of  the  fact  that  certain  portions  or  fractions  coming  over 
at  a  given  temperature  are  separated  from  other  fractions 
obtained  at  a  different  temperature.  Below  150°  C.  the 
fraction  distilling  out  is  called  gasoline;  150°  to  300°,  ker- 
osene; then  successive  fractions  of  heavy  burning  oil,  par- 
affin oil,  lubricating  oil,  vaseline,  and  paraffin.  After  the 


166  APPLIED    CHEMISTRY 

volatile  products  are  all  off  from  the  paraffin  oils  a  con- 
siderable quantity  of  petroleum  coke  remains,  light  and 
porous,  which  forms  a  very  excellent  fuel.  These  various 
fractions  may  be  still  further  subdivided  if  desired.  Gas- 
oline may,  by  taking  the  portions  coming  off  at  smaller 
intervals,  be  fractionated  into  petroleum  ether,  rhigoline, 
'benzine,  naphtha  and  gasoline.  In  fact,  it  is  said  that 
some  of  the  refining  companies  make  over  one  hundred 
products  in  distilling  paraffin-base  oils.  At  present  the 
demand  made  by  motor  cars  and  other  machines  using 
gas  engines  is  mostly  for  gasoline.  Unfortunately,  the 
percentage  of  this  in  crude  oil  is  not  high.  Of  late  years 
the  great  problem  has  been  to  devise  some  way  of  convert- 
ing the  heavier  portions  of  the  oils  into  the  lighter.  This 
is  called  " cracking"  and  various  plans  have  been  sug- 
gested, some  of  which  are  fairly  successful.  Thus  a  very 
considerable  amount  of  gasoline,  although  not  present 
originally  in  the  oil,  may  be  obtained  from  most  good 
varieties  of  petroleum. 

11.  Natural  Gas. — If  sawdust  or  powdered  soft  coal 
is  put  into  a  test  tube  and  heated,  not  merely  is  there 
an  oily  substance,  having  the  odor  of  tar,  driven  off, 
but  gaseous  products  as  well,  which  are  combustible. 
So,  in  the   earth  when  the  buried  forests  were  being 
subjected  to  heat,  these  gaseous  products  were  expelled. 
Probably  vast  quantities  escaped  and  were  lost;  other 
portions  were  caught  beneath  impervious  layers  of  rock 
and  furnish  the  natural  gas  of  today.     Some  of  it  may 
be  due  to  the  chemical  action  of  water  upon  carbides 
that  were  formed,  but  this  will  be  considered  at  another 
time. 

12.  Charcoal. — Formerly   charcoal   was   made   in   the 
characteristic  wasteful  American  way.     Great  piles  of 
wood  were   covered  writh   earth  and   sod  with  several 


CARBON  1 67 

openings  at  the  bottom  to  allow  the  entrance  of  air.  The 
wood  was  then  set  on  fire  and  the  lower  portions  in 
burning-  expelled  the  volatile  products  from  the  upper 
portion,  forming  charcoal.  At  the  present  time,  with 
our  rapidly  disappearing  forests,  the  wood  in  suitable 
lengths  is  put  into  iron  retorts  and  heated  from  beneath 
by  means  of  coal.  By  this  plan  not  only  is  a  cheaper 
fuel  used,  but  various  valuable  by-products,  such  as  wood 
alcohol,  acetone  and  acetic  acid  are  saved,  with  a  value 
probably  as  great  as  that  of  the  charcoal  itself.  There  is 
great  demand  also  for  boneblack,  a  charcoal  made  from 
bones.  During  the  last  year  of  the  war  there  was  ur- 
gent need  also  for  all  the  nut  charcoal  obtainable.  This 
is  made  from  cocoanut  shells,  and  all  other  nuts,  even 
from  the  pits  of  the  peach,  apricot  and  other  similar 
fruits.  This  variety  of  charcoal  is  by  far  the  most  ab- 
sorptive of  any  and  was  used  in  making  gas  masks. 

13.  Uses  for  Charcoal. — Besides  the  special  temporary 
use  of  nut  charcoal  just  mentioned,  it  has  some  use  at 
all  times  in  research  chemical  laboratories  in  absorbing 
and  separating  small  quantities  of  rare  gases  such  as 
those  found  in  the  air  belonging  to  the  argon  group. 
Boneblack  of  all  the  charcoals  is  probably  the  most  ex- 
tensively used.  Its  chief  value  is  in  refining  sugar.  The 
syrup,  brown  in  color,  is  passed  through  charcoal  filters 
whereby  the  color  is  removed.  A  special  form  of  bone- 
black,  known  as  ivory  ~black,  made  from  the  horns  and 
tusks  of  animals,  is  used  considerably  as  a  black  paint. 
Wood  charcoal  is  sometimes  used  as  a  fuel  in  open  fires; 
als:o  in  filters  for  cisterns  in  suburban  and  country  homes. 
If  so  used  it  should  be  removed  at  intervals,  and  heated  to 
redness  to  destroy  any  organic  matter  collected  within 
the  pores.  By  doing  this  it  is  again  fit  for  service.  For 
water  in  a  cistern  already  contaminated  a  bag  of  char- 


168  APPLIED    CHEMISTRY 

coal  suspended  in  the  water  for  a  few  days  is  sometimes 
helpful. 

14.  Lamp  Black. — This  is  a  finely  divided  form  of  car- 
bon obtained  by  burning  in  a  limited  supply  of  air  some 
oil  or  gas  containing  carbon  and  hydrogen.    The  hydro- 
gen burns,  but  most  of  the  carbon  is  deposited  as  a  soot. 
It  is  the  best  black  paint  known  when  ground  in  oil. 
It  is  also  the  main  ingredient  of  printers'  ink. 

15.  Coke. — Coke  is  made  by  heating  coal  in  iron  re- 
torts, as  described  for  making  charcoal,  or  in  specially 
constructed  ovens.     When  prepared  in  retorts  the  vola- 
tile products  are  saved  and  utilized  as  will  be  described 
later:  from  ovens  the  volatile  gases  are  often  allowed 
to  escape  thus  involving  great  financial  loss,   as  fully 
one-fourth  the  fuel  value  is   contained  in   the   volatile 
portions.     Coke  is  a  dark,  or  steel-gray,  porous  solid, 
which  burns  with  intense  heat.     It  is  used  in  iron  and 
other  smelters  because  of  its  fuel  and  reducing  values. 

16.  Gas  Carbon. — On  the  interior  of  retorts  used  in 
making  coke   a  fine-grained  form   of   carbon  is  slowly 
deposited.     At  intervals  this  is  removed,  molded  into 
sticks  and  plates,  and  used  in  arc  lights,  battery  plates 
and  similar  other  electrical  work. 

17.  Carbon  Monoxide. — Carbon  forms  two  oxides,  the 
monoxide,  CO,  and  the  dioxide,  C02.     The  latter  is  al- 
ways produced  in  the  combustion  of  carbon  when  the 
supply  of  oxygen  is  plentiful ;  when  insufficient  the  for- 
mer is  the  result.    Little  thought  is  usually  given  to  the 
lower  oxide,  but  on  account  of  its  poisonous  properties 
it  demands  a  very  careful  study.    It  may  find  access  to 
the  home  in  various  ways.     Most   modern  houses   are 
heated  by  hot-air  furnaces,  usually  made  of  cast  iron. 
Fig.  38  shows  the  construction.     The  air  enters  freely 
through  the  ash-pit  and  in  the  lower  portions   of  the 


CARBON 


169 


firebox  carbon  dioxide  is  produced.  As  this  passes  up 
through  the  layers  of  red-hot  carbon,  where  there  is  no 
air,  carbon  monoxide  is  formed,  thus, 

CO,  +  C  ->  2CO. 

Then  as  the  monoxide  flows  into  the  space  above  the 
fire  it  again  meets  oxygen  entering  through  the  drafts 
and  about,  the  door.  Hence,  it  burns  and  forms  carbon 
dioxide  again,  thus, 

2CO  +  0,,  ->  2C(X. 


Fig.   38. — Formation   of   carbon   monoxide   in   a    furnace. 

The  flickering  blue  flames  of  burning  carbon  monoxide 
may  plainly  be  seen  in  a  furnace  into  which  no  coal 
has  been  thrown  for  some  time.  Likewise,  most  of  the 
time  it  may  be  seen  in  base  burners  which  use  hard 
coal.  Under  conditions,  as  just  described,  no  carbon 
monoxide  remains  and  the  products  of  combustion  are 
carried  out  through  the  flue  to  the  air.  There  are  times, 
however,  when  this  is  not  true.  At  night,  in  banking  the 
fire  so  that  it  will  keep  well  till  morning,  usually  con- 


170  APPLIED    CHEMISTRY 

siderable  coal  is  put  into  the  firebox.  Now,  when  the 
carbon  monoxide  formed  in  the  interior  of  the  fire 
reaches  the  open  space,  it  has  been  cooled  by  the  layer 
of  coal  on  top  to  such  an  extent  that  it  does  not  burn. 
It  is  then  occluded  or  absorbed  by  the  hot  iron  of  the 
furnace  as  is  hydrogen  by  platinum  or  palladium. 
Quickly  it  passes  through  to  the  air  space  about  the  fur- 
nace and  is  carried  by  the  ascending  currents  into  the 
living  rooms  above.  The  same  thing  occurs  with  base 
burners  when  the  coal  is  shaken  down  in  considerable 
quantities  from  the  reservoir  above.  Gas  heaters,  when 
improperly  regulated,  as  may  be  known  by  the  flame 
being  yellow,  often  produce  carbon  monoxide,  and  to- 
bacco smoke  always  contains  a  considerable  quantity 
of  the  poisonous  gas.  In  lighting  with  gas,  if  the  man- 
tle is  being  blackened  by  a  deposit  of  soot,  carbon  mon- 
oxide is  invariably  being  formed;  a  cook  stove,  burning 
with  a  yellow  flame,  is  not  receiving  sufficient  air  for 
perfect  combustion,  and  in  all  probability  is  producing 
some  carbon  monoxide.  The  burned  gases  from  a  motor 
car  or  other  similar  gas  engine,  especially  if  the  engine 
is  running  "idle,"  contain  considerable  quantities  of 
carbon  monoxide. 

18.  Characteristics  of  Carbon  Monoxide. — It  is  a  col- 
orless gas,  of  nearly  the  same  density  as  air.  It  has  a 
peculiar,  somewhat  disagreeable  but  very  faint  odor.  It 
may  be  liquefied  at  -190°  C.  It  burns  with  a  pale  blue 
flame,  producing  carbon  dioxide.  From  this  fact,  that 
it  is  able  to  take  up  more  oxygen,  it  is  a  reducing 
agent  and  often  serves  thus  in  the  separation  of  metals 
from  their  oxides.  This  is  notably  the  case  with  iron, 
shown  by  the  equation, 

Fe203  +  3CO  -»  2Fe  +  3C02. 


CARBON  171 

Carbon  monoxide  is  very  poisonous.  When  inhaled  it 
forms  a  compound  with  the  hemoglobin  which  prevents 
the  carrying  of  oxygen  to  the  tissues.  Thus  even  in 
moderate  amounts,  it  causes  serious  results,  asphyxiation 
and  death.  Most  fatalities  reported  from  asphyxiation 
by  the  exhaust  from  motor  cars  in  a  closed  garage  are 
due  to  the  poisonous  effects  of  carbon  monoxide.  Years 
ago,  in  the  warmer  countries  of  Europe,  open  charcoal 
fires  were  the  common  method  of  heating  the  homes, 
and  many  cases  of  death,  accidental  or  otherwise,  are  on 
record  due  to  putting  considerable  charcoal  on  top  of 
the  fire  and  retiring.  Knowing  the  poisonous  charac- 
ter of  the  gas  no  one  should  sleep  in  a  room  warmed  by 
a  furnace  with  the  register  left  open,  and  even  thus, 
the  windows  should  be  raised.  In  the  case  of  other 
sources  of  the  gas,  as  already  mentioned,  steps  should 
be  taken  at  once  to  remove  the  cause.  Following  ex- 
plosions in  coal  mines,  quantities  of  carbon  monoxide 
exist,  called  by  the  miners  " after  damp"  or  "black 
damp."  Usually  it  is  the  cause  of  the  greater  number 
of  fatalities. 

19.  Carbon  Dioxide. — This  gas  has  already  been  men- 
tioned as  a  constituent  of  the  air.     It  results  from  the 
decomposition  of  organic  matter,  from  combustion  and 
from  respiration.    All  of  these  sources  furnish  very  con- 
siderable amounts,  but  the  proportion  of  three  or  four 
parts  per  ten  thousand  of  air  remains  practically  con- 
stant, due  to  the  action  of  plant  life. 

20.  Preparation. — Carbon  dioxide  in  the  laboratory  or 
for  commercial  purposes  is  usually  obtained  by  the  re- 
action of  some  carbonate,  as  limestone  or  marble,  with 
an  acid,  generally  h}rdrochloric.    The  equation  is 

CaC03  +  2HCl  -*  C02  +  H20  +  CaCl2. 


172  APPLIED    CHEMISTRY 

It  may  be  collected  either  by  downward  displacement 
or  over  water;  for  commerce  it  is  compressed  in  steel 
cylinders. 

21.  Characteristics. — Carbon  dioxide  is  a  colorless, 
odorless  gas  with  a  density  about  once  and  a  half  that  of 
the  air.  This  may  be  shown  by  pouring  the  gas  from 
a  wide-mouthed  liter  bottle  into  the  upper  end  of  a 
trough  in  which  are  some  short  burning  candles  as 
shown  in  Pig.  39.  The  gas  cannot  be  seen,  but  one 
candle  after  another  is  extinguished  as  the  carbon  di- 
oxide flows  down.  A  liter  bottle  is  usually  sufficient  to 
make  the  experiment  three  times  in  succession.  The  gas 


Fig.    39. — Pouring   carbon    dioxide    upon   burning    candles   in    a   trough. 

is  soluble  in  water,  about  volume  for  volume  at  ordi- 
nary temperatures.  At  -79°  C.  it  may  be  liquefied;  if 
the  liquid  be  allowed  to  escape  rapidly,  the  lowering  of 
temperature  caused  by  the  evaporation  converts  a  con- 
siderable amount  of  the  liquid  into  a  white  solid,  resem- 
bling snow,  which  vaporizes  without  melting,  just  as  io- 
dine crystals  do.  Mixed  with  ether,  solid  carbon  dioxide 
is  often  used  as  a  freezing  mixture ;  with  it  mercury 
may  be  easily  solidified  and  many  other  interesting  ex- 
periments performed.  Carbon  dioxide  will  not  burn 
and  is  so  stable  that  with  very  few  exceptions  it  cannot 


CARBON  173 

be  decomposed  by  a  burning  metal.  Magnesium  rib- 
bon, ignited  and  thrust  into  a  bottle  of  the  gas,  con- 
tinues to  burn  with  the  formation  of  magnesium  oxide 
and  free  carbon.  Both  products,  being  solids,  may  be 
seen  upon  the  sides  of  the  bottle.  The  equation  illus- 
trating the  action  is 

2Mg  +  C02  ->  C  +  2MgO. 

When  dissolved  in  water  some  portion  of  the  gas  reacts 
chemically,  forming  a  weak  and  unstable  acid,  thus, 

C02  +  H20  i=*  H2C03. 

Under  pressure,  carbon  dioxide  obeys  Henry's  law,  that 
the  amount  of  gas  dissolved  by  a  liquid  is  proportional  to 
the  pressure.  That  is,  at  five  atmospheres'  pressure  a  liter 
of  water  would  dissolve  five  times  as  much  gas  as  at  one 
atmosphere. 

22.  Uses. — The  purpose  of  the  small  amount  of  carbon 
dioxide  in  the  air  has  already  been  mentioned.  Soda 
water,  so  called,  is  familiar  to  all.  It  is  water  charged 
with  the  gas  under  two  or  three  atmospheres'  pressure; 
as  soon  as  this  is  relieved  the  gas  begins  to  escape  with 
the  familiar  effervescence.  Most  soft  drinks  in  bottled 
form  are  thus  carbonated.  Carbon  dioxide,  liquefied  in 
tiny  steel  capsules,  called  "sparklets,"  may  be  had  from 
the  supply  houses.  They  are  to  be  used  for  the  carbon - 
ation  of  water  either  at  home  or  in  camp;  for  this  a 
specially  designed  apparatus  is  necessary,  which  allows 
the  escape  of  the  gas  into  the  bottle  of  water  by  piercing 
the  cap  with  a  stiff  needle.  Two  sizes  are  made,  suffi- 
cient for  the  carbonation  of  a  pint  or  a  quart  of  water. 
The  chemical  fire  extinguisher,  seen  often  in  the  hall- 
ways of  public  buildings,  and  larger  sizes  upon  fire 
trucks,  makes  use  of  carbon  dioxide.  Fig.  40  gives  a 
sectional  view.  Water  is  put  into  the  vessel,  made  of 


174  APPLIED    CHEMISTRY 

copper  or  brass,  up  to  the  shoulder ;  in  this  a  pound  or  a 
pound  and  a  half  of  baking  soda  is  dissolved.  In  the 
tank  near  the  top  supported  in  a  wire  frame  is  a  bottle 
partially  filled  with  sulphuric  acid.  The  stopper  of  this 
bottle  fits  very  loosely  so  that  it  readily  drops  out  if  in- 
verted. For  use  the  whole  apparatus  is  turned  upside 
down;  the  acid  flows  out  into  the  soda  solution,  and 
reacting  with  the  bicarbonate  generates  carbon  dioxide 


Fig.   40. — Babcock   fire   extinguisher. 

rapidly:  the  pressure  thus  obtained  throws  the  water 
charged  with  gas  upon  the  fire.  The  reaction  is  shown 
by  the  equation, 

NaHC03  +  H2S04  ->  C02  +  H20  +  NaHS04. 
The  effect  of  carbon  dioxide  may  be  illustrated  by  a  lit- 
tle experiment  upon  the  lecture  table.     A  small  evap- 


CARBON  175 

orating  dish  partly  filled  with  gasoline  is  ignited;  it 
may  be  instantly  extinguished  by  pouring  carbon  di- 
oxide from  a  wide  mouthed  liter  bottle.  Usually  a  liter 
of  gas  is  sufficient  to  repeat  the  experiment,  twice. 

23.  The  Test  for  Carbon  Dioxide.— On  account  of  its 
density  carbon  dioxide  often  collects  in  old,  long-unused 
wells  and  shafts.    Although  it  is  not  poisonous,  one  may 
drown  in   it  as   quickly  as   in  water.     It  is  necessary, 
therefore,  to  test  the  air  before  entering  places  where 
it  may  have  accumulated.     This  may  be  done  by  lower- 
ing a  lantern :  if  it  continues  to  burn  well,  the  air  is 
safe  to  breathe.     In  the  laboratory  carbon   dioxide   is 
tested   by  bubbling  it  into  lime   water,   with   which   it 
forms  a  milky  white  precipitate.     If  the  operation  be 
long  continued  the  precipitate  redissolves,  thus, 

Ca(HO)2  +  C02  ->  CaC03  +  H20. 
The  white  precipitate  is  calcium  carbonate 
CaC03  +  H20  +  C02  -»  CaH2(C03)2. 

The  product  formed  by  the  continued  action  is  acid  cal- 
cium carbonate  which  is  soluble  in  water,  hence  the  ex- 
planation of  the  disappearance  of  the  precipitate. 

24.  Other  Carbon  Compounds. — Carbon  tetrachloride, 
as  the  name  would  indicate,  has  the  formula,  CC14.    It  is 
a  slightly  yellow,  oily  liquid,  heavier  than  water,  not  in- 
flammable, an  excellent  solvent  for  oils  and  grease,  and 
at  present  not  very  expensive.     It  may,   therefore,   be 
used  instead  of  gasoline  with  perfect  safety  for  cleaning 
garments.     "Carbona,"   a   largely   advertised   cleaning 
compound,    is   mostly   carbon    tetrachloride.      While    it 
contains  some  benzine   there  is  not   sufficient   quantity 
to  render  the  mixture  inflammable.     "Pyrene,"  a  well- 
known  fire   extinguisher,   frequently   carried  by  motor 
car  owners  in  small  cylinders,  is  largely  carbon  tetra- 


176  APPLIED    CHEMISTRY 

chloride.  It  is  readily  vaporized,  and  as  the  gas  is  heavy 
and  not  inflammable  it  extinguishes  the  fire  by  shutting 
off  the  oxygen  supply.  Silicon  carbide,  SiC,  made  by 
fusing  in  an  electric  furnace  a  mixture  of  sand  and  coke 
with  common  salt,  is  a  crystalline  solid  of  a  dark  gray 
or  purple  color.  The  reaction  is  shown  thus, 

Si02  +  30  -»  2CO  +  SiC. 

The  compound  is  said  to  be  even  a  shade  harder  than 
the  diamond  and  is  used  extensively  under  the  name, 
carborundum,  as  an  abrasive.  It  is  made  into  whetstones, 
wheels,  and  a  great  variety  of  other  forms  for  cutting  and 
polishing.  Another  very  valuable  carbide  is  made  by  fus- 
ing in  an  electric  furnace  a  mixture  of  lime  and  coke,  thus, 

CaO  +  3C  -»  CaC2  +  CO. 

It  is  known  as  calcium  carbide  and  is  used  extensively  as 
mentioned  elsewhere  for  the  preparation  of  acetylene. 

Exercises  for  Review 

1.  What  can  you  say  of  the  importance  and  total  quantity  of 
carbon  in  nature?     Name  some  of  the  many  forms  in  which  it  oc- 
curs, as  compounds. 

2.  Classify  the  forms  of  carbon. 

3.  Give  proof  that  the  diamond  is  carbon. 

4.  Give  an  account  of  Moissan's  experiment  in  making  diamonds. 

5.  Give  the  chief  characteristics  and  practical  uses  of  the   dia- 
mond. 

6.  Compare  graphite  with  diamond.    Give  several  important  uses. 

7.  Classify  the  coals.     What  is  their  origin?     Why  so  different? 

8.  What  is  the   origin  of  petroleum?     Name   two   kinds.     Why 
so  called? 

9.  What   is   fractional   distillation?     What   use   is -made   of   it? 
What  is  meant  by  "cracking"  an  oil? 

10.  Name   some  of  the  valuable  products  obtained  from  petro- 
leum. 

11.  What  is  the  probable  origin  of  natural  gas? 

12.  How  is  charcoal  made  and  what  by-products  are  obtained? 


CARBON  177 

!.'>.  Name  several  varieties  of  charcoal  and  give  uses  of  each. 

14.  What  is  ivory  black?     Lamp  black?     Uses  of  each? 
1-").  How  is  coke  prepared?     Its  chief  uses? 

l(i.  What  is  the  source  of  gas  carbon?     What  uses  has  it? 
17.  Name   several   ways  in   which  carbon  monoxide   may  find  its 
way  into  the  home.     Give  the  details  of  one  case. 

15.  Describe  carbon  monoxide.     Its  effects  upon  the  blood. 
1!>.  Give  the  sources  of  carbon  dioxide  in  the  air. 

20.  How  is  carbon  dioxide  made  for  commerce?     Equation. 

21.  Give  chief  properties  of  carbon  dioxide. 

22.  Name  some  important  uses  for  carbon  dioxide. 

2'>.  Describe   the   chemical   fire   extinguisher.     Give  the  chemical 
reaction. 

24.  Give  two  tests  for  carbon  dioxide. 

25.  What  valuable  uses  has  carbon  tctrachloride?     Name   some 
commercial  forms  in  which  it  appears. 

2(5.  Name  two  carbides,  state  how  made  and  uses  of  them. 


CHAPTER  XIII 

VALENCE 
Outline- 
Meaning  of  Valence 
Degrees  of  Valence 
Valence  of  Eadicals 
Variation  of  Valence 

Saturated  and  Unsaturated  Compounds 
Valence  in  Ternary  Compounds 

1.  Meaning  of  Term. — As  used  in  chemistry  the  term 
valence  means  the  power  an  atom  has  of  combining  with 
one  atomic  weight  of  hydrogen  or  its  equivalent.    Thus,  in 
hydrogen  chloride,  one  atomic  weight  of  chlorine  combines 
with  one  of  hydrogen.     As  the  hydrogen  atom  serves  as 
the  unit,  chlorine  must  have  a  valence  of  one;  likewise, 
do  bromine,  fluorine  and  iodine.    Radicals,  not  being  com- 
pounds but  groups  serving  like  atoms,  as  parts  of  a  com- 
pound, likewise  have  valence.   Thus,  chloric  acid,  HC1O3, 
shows  that  the  group  -C103  has  a  valence  of  one ;  so,  also, 
ammonium,  NH4-,  in  ammonium  chloride;  -N03  in  ni- 
tric acid;  -HO  in  sodium  hydroxide  and  several  others. 
As  the  metals  are  electropositive  and  do  not  form  any 
familiar  compounds  with  hydrogen,  their  valence  must 
be   determined  by  examining  some  such  compound  as 
their  chlorides.     Thus,  common  salt,  NaCl,  shows  that  so- 
dium has  a  valence  of  one ;  KC1,  that  potassium  has  a  val- 
ence of  one.    All  atoms  or  groups  having  a  valence  of  one 
are  said  to  be  univalent  or  are  sometimes  called  monads. 

2.  Valence  Greater  than  One. — If  we  examine  the  for- 
mula for  the  water  molecule,  we  see  that  oxygen  has 
combined  with  two  atoms  of  hydrogen,  hence  oxygen  is 

178 


VALENCE  179 

said  to  have  a  valence  of  two.  Similarly,  magnesium  as 
seen  in  magnesium  oxide,  MgO,  copper  in  copper  oxide, 
CuO,  calcium  in  lime,  CaO,  all  have  a  valence  of  two 
and  are  called  bivalent  or  diads.  Aluminum  and  iron 
as  shown  by  the  formulas,  A1G13  and  FeCl3,  are  trivalent 
or  triads;  while  carbon,  as  seen  in  carbon  dioxide  or  car- 
bon tetrachloride,  and  silicon  in  silicon  dioxide,  Si02,  are 
tetrads  or  quadrivalent.  Phosphorus  as  seen  in  the  com- 
pounds P205  and  arsenic  in  As205  are  pentads. 

3.  Radicals   of   Valence   Higher   than   One. — In   sul- 
phuric acid,  H2S04,  sodium  carbonate,  Na2C03,  and  po- 
tassium chromate,  K2Cr04,  are  seen  radicals  combining 
with  two  univalent  atoms;  hence,  -SO4,  -Cr04  and  -C03 
must  be  bivalent.    Likewise,  -P04  and  -B03,  seen  in  the 
phosphoric  and  boric  acids,  H3P04  and  IT3B03,  are  tri- 
valent ;  while  -Si04  found  in  orthosilicic  acid,  II4Si04, 
is  quadrivalent. 

4.  Variation  in  Valence. — Nitrogen   and  phosphorus 
are  spoken  of  above  as  being  quinquivalent.     Their  ox- 
ides indicate   this.     But  they  also   form  the  hydrogen 
compounds,    ammonia,    NH3,    and    phosphine,    PH3,    in 
which  a  valence  of  three  is  indicated.     In  another  chap- 
ter, copper  is  seen  to  form  two  compounds,  as  also  mer- 
cury,   CuO    and    Cu20,    HgCl2    and   Hg2Cl2,    indicating 
sometimes  a  valence  of  one,  sometimes  of  two.     Many 
other  cases  might  be  cited,  notably  carbon  in  carbon 
monoxide   and  the   dioxide,   also   marsh   gas,   CH4,   and 
ethylene,  C2H4.     In  the  case  of  the  carbon  atom  the  va- 
lence is  universally  regarded  as  four  and  such  compounds 
as  ethylene,   C2H4,   acetylene,   C2H2,   and  the   monoxide 
are  said  to  be  unsaturated.     By  this  is  meant  that  the 
carbon  atom  in  such  compounds  has  not  combined  with  all 
that  it  is  capable  of  holding.    There  is  abundant  evidence 
that  this  is  true.    We  have  seen  already  in  the  case  of  the 


180  APPLIED    CHEMISTRY 

carbon  monoxide  that  it  readily  combines  with  another 
atom  of  oxygen  forming  the  dioxide;  also, -that  inhaled  it 
completes  the  saturation  by  combining  with  the  hemoglo- 
bin of  the  blood ;  likewise,  it  readily  unites  with  two  atoms 
of  chlorine  to  form  phosgene,  COC12.  Other  very  re- 
markable and  interesting  proofs  for  the  carbon  com- 
pounds are  abundant.  One  of  these  is  the  passage  of  the 
gas  through  a  solution  of  bromine  in  water  or  through 
a  quantity  of  bromine  beneath  a  layer  of  water  to  prevent 
its  escape  into  the  air.  Marsh  gas,  CH4,  if  carbon  has  a 
valence  of  four,  would  be  a  saturated  compound.  When 
it  is  slowly  bubbled  through  bromine,  no  matter  how  long 
continued,  the  escaping  gas  has  all  the  properties  of 
marsh  gas  and  the  bromine  remains  unchanged.  On  the 
other  hand,  if  ethylene,  C2H4,  be  used  in  the  same  way, 
the  bubbles  in  passing  through  seem  to  become  smaller 
as  if  they  were  being  absorbed,  and  after  an  hour  or  two, 
the  red  color  of  the  bromine  has  entirely  disappeared, 
and  in  its  place  is  a  colorless,  oily  liquid,  of  pleasant  odor, 
without  the  slightest  resemblance  to  bromine.  An  analy- 
sis of  this  liquid  shows  that  it  contains  two  atomic 
weights  of  bromine  per  molecule,  as  would  be  represented 
by  the  formula,  C2H4Br2.  If  written  graphically,  which 
shows  the  structure  or  arrangement,  marsh  gas  is 

H  H  H 

I  I     I 

H-O-H,  ethylene,  -C-C-,  and  the  bromine  compound, 

H  H  H 

H  H 

I     I 
Br-C-C-Br.    These  formulas  show  that  in  marsh  gas,  the 

H  H 

carbon  atom  has  all  its  bonds  saturated  with  hydrogen: 
that  in  ethylene  there  are  two  not  so  used  and  it  is  to 


VALENCE  181 

these  that  the  bromine  lias  been  attached.  A  very  large 
number  of  other  similar  experiments  have  been  made, 
all  of  which  seem  to  show  the  truth  of  the  position  taken. 
Likewise,  in  the  case  of  most  of  the  seeming  variations  in 
valence,  one  or  more  of  the  compounds  are  unsaturated 
ones.  Thus  nitrogen  in  ammonia,  NH3,  seems  to  have  a 
valence  of  three ;  but  ammonia  readily  forms  additional 
compounds,  as  when  it  is  brought  into  contact  with  hydro- 
chloric acid,  thus, 

NH3  +  HC1  -»  NH4C1. 

In  the  last  compound  the  nitrogen  atom  is  combined  with 
five  univalent  atoms.  Likewise,  ammonia  combines  addi- 
tively  with  nitric  acid, 

NH3  +  HN03  ->  NH4N03, 

in  which  compound  the  nitrogen  atom  is  combined  with 
four  univalent  atoms  and  one  univalent  group.  Mercury 
in  mercurous  chloride,  Hg2Cl2  has  apparently  a  valence  of 
one,  while  in  mercuric  chloride,  HgCL,  it  is  evidently  two. 
In  all  probability  the  mercury  atom  always  has  a  valence 
of  two,  and  any  compounds  not  indicating  such  are  unsat- 
urated. It  is  well  known  that  mercurous  salts  readily 
take  up  more  of  an  electronegative  element  or  group 
and  become  mercuric  compounds.  Thus,  many  other 
cases  might  be  considered  but  for  the  present  these  seem 
sufficient. 

5.  Ternary  Compounds. — Sometimes  it  becomes  de- 
sirable to  determine  the  valence  of  an  element  in  a  com- 
pound, knowing  the  formula.  In  binary  compounds, 
if  the  valence  of  one  of  the  elements  is  known,  the 
other  is  evident  at  a  glance.  In  ternary  compounds 
this  is  not  true.  However,  if  it  is  known  that  the  valence 
of  the  oxygen  atoms  is  equivalent  to  the  added  valences 
of  the  other  atoms  present,  it  becomes  easy.  To  illus- 


182  APPLIED    CHEMISTRY 

trate,  sulphuric  acid  has  the  formula,  H2S04.  It  is  de- 
sired to  know  the  valence  of  the  sulphur  atom  in  the 
compound.  There  are  four  oxygen  atoms  whose  total 
valence  is  8;  the  two  hydrogen  atoms  have  a  valence 
of  2 ;  hence,  2  +  S  =  8,  from  whicli  sulphur  must  be  6. 
In  potassium  dichromate,  K2Cr207,  the  equation,  2  +  2Cr 
=  14,  indicates  the  several  valences,  from  which  chro- 
mium is  found  to  be  six. 

Exercises  for  Review 

1.  Define  and  illustrate  valence. 

2.  Name   some  elements  with   a  valence   of   one;    some   radicals 
with  the  same  valence. 

3.  Name  some  elements  with  valence  of  two;  also  some  radicals. 

4.  What  names  are  given  to  elements  with  valence  of  one,  two, 
three,  etc.? 

5.  What  is  meant  by  an  unsaturated  compound?     Name  two. 

6.  Give   some   experimental  proof   that   ethylene  is  unsaturated, 

7.  What  facts  indicate  that  carbon  monoxide  is  unsaturated? 

8.  What  is  a  structural  or  graphic  formula?     What  advantage 
has  it? 

9.  Wliat  evidence  is  there  that  ammonia  is  unsaturated? 

10.  Find  the  valence  of  chromium  in  K,CrO4;  nitrogen  in  HNO3; 
manganese  in  KMnO4 ;   iron  in  Fe2O3 ;   phosphorus  in  P2O5 ;   phos- 
ph-orus  in  H3PO4. 


CHAPTER  XIV 

ILLUMINATING  AND  FUEL  GASES 

Outline- 
Natural  Gas 
Acetylene 
Pintsch  Gas 
Blau  Gas 
Coal  Gas 
Water  Gas 

1.  Natural   Gas. — This    has   already   been   mentioned 
and  its  supposed  origin.    Another  theory  has  been  sug- 
gested by  some  which  may  possibly  account  for  at  least 
a  part  of  the  natural  supply.     Two  carbides  have  been 
mentioned  in  the  preceding  chapter.     One  of  them  re- 
acts with  water,  as  will  be  seen,  to  form  a  combustible 
gas.     Another,  aluminum  carbide,  does  likewise.     It  is 
thought  that  at  some  time  in  the  past  this  carbide  has 
been   formed   in   the   earth   and   that   water   coming  in 
contact  with  it  reacts  forming  marsh  gas,  which  is  the 
main   constituent    of   natural   gas.      The    reaction   with 
water  is  here  shown, 

A14C3  +  12H20  -»  3CH4  +  2Al2(HO)a.       . 

2.  Acetylene. — For  commercial  purposes,  acetylene  is 
always  prepared  by  the  reaction  of  water  upon  calcium 
carbide,  thus, 

CaC2  +  2H20  ->  C2H2  +  Ca(HO)2. 

Owing  to  the  high  percentage  of  carbon  in  the  gas,  it 
cannot  be  used  in  an  ordinary  burner,  for  the  insuffi- 
cient amount  of  air  supplied  results  in  a  very  smoky 
flame.  A  special  tip,  shown  in  Fig.  41,  is  designed  so 

183 


184  APPLIED    CHEMISTRY 

as  to  draw  in  the  air  by  two  minute  jets  of  gas  directed 
toward  each  other.  Burned  thus,  a  brilliant  white  light 
is  obtained  with  only  about  one-fifth  the  quantity  of  gas 
consumed  as  in  other  common  burners.  It  is  thus  used 
extensively  in  motor  cycles :  for  this  purpose  it  is  con- 
tained in  the  familiar  "Prestolite"  tank.  At  first,  at- 
tempts wrere  made  to  use  acetylene  in  liquefied  form, 
but  it  was  found  under  such  pressures  to  be  readily 
explosive  and  many  accidents  occurred.  It  is  very  solu- 
ble in  acetone,  a  liquid  of  pleasing  odor  obtained  in 
the  destructive  distillation  of  wood  in  making  charcoal. 
The  prestolite  tank  applies  this  principle :  large  quan- 


Fig.  41. — Acetylene  burner. 

tities  of  acetylene  under  several  atmospheres  pressure 
are  dissolved  in  the  acetone  in  the  tank  and  in  this  form 
it  is  perfectly  safe.  On  use  the  gas  escapes,  but  the 
acetone  remains  and  may  be  recharged.  For  cooking 
purposes  special  plans  must  be  had  for  furnishing  in- 
creased quantities  of  air,  otherwise  the  cooking  vessels 
become  heavily  coated  with  soot.  At  the  present  time 
acetylene  is  used  extensively  in  country  churches  and 
suburban  homes  both  for  lighting  and  cooking.  There 
are  several  types  of  generators,  but  the  most  satisfac- 
tory is  one  in  which  the  carbide  in  coarse  grains  drops 
slowly  into  a  considerable  quantity  of  water.  The  gas 


ILLUMINATING    AND    FUEL    GASKS  185 

is  piped  throughout  the  house  in  the  usual  way  and 
burned  in  tips  like  the  one  described  above.  The  most 
valuable  use  of  acetylene  at  the  present  time  is  for 
welding  and  similar  work  where  great  heat  is  required. 
The  gas  is  used  in  a  torch  such  as  was  described  for  oxy- 
hydrogen  work,  and  when  properly  adjusted  burns  with 
a  pale  blue,  intensely  hot  flame.  Even  when  air  in- 
stead of  oxygen  is  used,  furnished  with  a  foot  bellows, 
iron  wire,  such  as  is  used  in  baling  hay,  may  be  burned 
rapidly  in  the  air  with  a  beautiful  and  dazzling  shower 
of  sparks.  In  welding,  the  broken  object  is  heated,  the 
crack  made  somewhat  larger;  then  a  rod  of  steel  is 
melted  in  the  oxyacetylene  flame  and  the  molten  steel 
allowed  to  flow  down  into  the  crack.  Welding  thus 
properly  done  is  said  to  make  the  object  as  strong  as 
at  the  beginning. 

3.  Pintsch  Gas. — This  gas  received  its  name  from  an 
Englishman  who   first  prepared  it   for  the  purpose   of 
lighting  the  stage  coaches  of  that  day.     At  the  present 
time    it    is    used    practically   nowhere    outside    railway 
coaches,  where  it  is  seen  in  clusters,  usually  enclosed  in 
glass  globes  at  the  ceiling.     It  is  prepared  from  some 
oil,  often  naphtha,  by  heating  sufficiently  high  to  decom- 
pose  it  into  gases  which  will  not  liquefy  again  upon 
cooling.     As  it  is  thus  made  from  a  refined  oil,  the  re- 
sulting gas  needs  little  purification,  other  than  the  re- 
moval of  a  little  tar  and  water.  It  is  carried,  heavily  com- 
pressed, in  cylinders  under  the  railway  coaches.     Unlike 
most  similar  gases,  the  compression  does  not  greatly  re- 
duce its  illuminating  powers. 

4.  Blau  Gas. — At  the  present  time  a  similar  gas,  called 
Blau  gas,  is  being  manufactured  from  a  less  refined  oil 
than   the  pintsch   uses.     It   is  purified  and  compressed, 
whereupon    some    of    the    constituents    become    liquid. 


186  APPLIED    CHEMISTRY 

These  are  removed  and  the  gas  is  then  stored  in  steel 
cylinders  under  high  pressure.  In  the  oxyhydrogen 
blowpipe  it  gives  intense  heat ;  it  is  also  used  in  subur- 
ban homes  for  cooking  and  lighting  purposes  as  other 
gases  are  in  the  city.  For  such  use  two  tanks  of  the 
compressed  gas  are  placed  in  a  container  outside  the 
building  and  attached  to  the  piping  of  the  house.  When 
one  is  exhausted  it  is  sent  to  the  factory  for  refilling  and 
the  other  put  in  service. 

5.  Coal  Gas. — Most  cities  in  sections  where  bitumi- 
nous coals  are  to  be  had,  use  large  quantities  of  coal 
gas.  It  is  prepared  by  heating  the  soft  coal  in  iron 
retorts  as  already  mentioned  for  making  coke.  The 
resulting  gaseous  mixture,  very  impure,  must  be  puri- 
fied before  being  suitable  for  use.  By  cooling,  first  the 
tar  is  removed  and  flows  into  a  tank  or  well  fitted  to  re- 
ceive it.  The  gas  next  passes  through,  usually,  two 
"towers,"  filled  with  lumps  of  coke  or  something  equiv- 
alent, kept  moist  by  water  trickling  over  it.  Here  the 
ammonia  is  removed.  The  gas  next  passes  through 
three  or  four  purifiers,  containing  lime  or  ferric  oxide, 
which  remove  other  compounds  like  sulphur  dioxide, 
hydrogen  sulphide  and  carbon  dioxide,  all  acidic  in 
character  and  either  not  combustible  or  very  undesir- 
able in  an  illuminating  gas.  Finally,  the  gas  is  metered 
and  passed  into  a  storage  tank  from  which  it  is  piped 
to  all  parts  of  the  city.  Remembering  that  coke  and 
gas  carbon  are  both  obtained  in  the  retorts  it  will  be 
seen  that  there  are  four  by-products  of  the  manufacture 
of  coal  gas.  Besides  the  two  just  named,  are  the  tar 
and  ammonia.  Tar  is  a  black,  viscous,  ill-smelling  liquid 
consisting  of  a  mixture  of  a  great  variety  of  compounds 
and  black  because  of  the  presence  of  some  free  carbon. 
From  it  are  made  several  colorless  liquids,  such  as 


ILLUMINATING    AND    FUEL    GASES  187 

aniline  and  toluol.  These  form  the  basis  of  an  indefi- 
nite number  of  other  compounds  of  the  very  greatest 
value:  photographic  developers,  such  as  hydroquinon; 
many  medicines,  like  aspirin;  all  the  great  variety  of 
beautiful  aniline  dyes;  phenol  or  carbolic  acid  and  its 
many  derivatives;  picric  acid  and  the  explosives  from 
it;  the  explosives  from  toluol,  and  hundreds  of  others. 

A  ton  of  coal  will  make  about  ten  thousand  cubic 
feet  of  gas  containing  one-fourth  to  one-third  the  fuel 
value  of  the  original  coal.  The  gas  consists  of  hydro- 
gen and  marsh  gas,  over  40  per  cent  of  each,  with  carbon 
monoxide,  and  ethylene  as  the  greater  part  of  the  bal- 
ance. Small  proportions  of  some  higher  hydrocarbons 
are  usually  present. 

6.  Water  Gas. — This  receives  its  name  from  the  fact 
that  steam  is  used  in  its  preparation.  Often  both  coal 
and  water  gas  are  manufactured  simultaneously  in  the 
same  building.  The  coke  obtained  as  a  by-product  in 
the  coal  gas  department  is  withdrawn  red-hot  from  the 
retorts  into  small  steel  cars  in  which  it  is  carried  quickly 
to  another  part  of  the  building.  Here  it  is  dumped 
through  a  trap  door  into  a  vertical,  cylindrical  retort 
on  the  floor  below.  A  blast  of  air  is  turned  on  the  hot 
coke  to  raise  its  temperature,  and  then  live  steam  is 
passed  through  it,  when  the  following  reaction  takes 
place, 

H20  +  C  ->  H2  +  CO. 

At  the  end  of  about  three  minutes  the  temperature  is 
too  low  to  effect  the  decomposition  of  the  steam,  which 
then,  automatically,  is  cut  off  and  the  air  again  turned 
on.  Thus,  in  three  minute  periods,  mechanically,  all 
day  the  steam  and  air  are  turned  on  alternately,  with 
results  as  shown  by  the  equation.  Both  the  constitu- 
ents thus  obtained  are  combustible,  but  a  gas  richer  in 


188  APPLIED    CHEMISTRY 

carbon  is  more  desirable.  Hence,  it  is  passed  through 
another  retort  containing  a  lattice  work  of  fire  brick 
heated  to  redness  by  a  gaseous  fuel.  Into  this  cham- 
ber is  sprayed  an  oil  obtained  from  petroleum,  which 
is  decomposed  as  was  described  in  making  pintsch 
gas.  These  products  are  mixed  with  the  two  already 
obtained  from  the  steam  and  coke,  such  that  the  final 
result  is  not  essentially  different  from  coal  gas.  The 
percentage  of  carbon  monoxide  is  higher,  hence  the  gas 
is  more  poisonous.  In  factories  making  both  coal  and 
water  gas  the  large  storage  tank  receives  both  usually 
in  something  like  the  proportion  of  3  of  water  to  two 
of  coal  gas.  In  other  cities  where  cheap  supplies  of  soft 
coal  are  not  available,  as  in  California,  a  gas  is  prepared 
from  crude  petroleum,  not  essentially  different  from  the 
coal  gas,  and  of  excellent  quality. 

Exercises  for  Review 

1.  Give  a  chemical  theory  for  the  formation  of  natural  gas.     Of 
what  does  natural  gas  consist? 

2.  How  is  acetylene  made?     Write  the  equation.     Describe  the 
tip  necessary  for  burning  it  successfully. 

3.  Describe  the  prestolite  system  of  lighting. 

4.  Why  not  use  liquefied  acetylene  for  lighting? 

5.  Give  some  important  uses  of  acetylene. 

6.  How  is  pintsch  gas  made?     Where  is  it  used? 

7.  How  is  blau  gas  made?     For  what  used? 

8.  Describe  the  process  of  making  coal  gas.     Name  the  impuri- 
ties removed  in  its  manufacture ;  also  the  by-products  obtained. 

9.  How  is  the  ammonia  recovered  and  purified? 

10.  What  are  some  of  the  products  obtained  from  tar? 

11.  What   are  gas  carbon  and  coke  used  for? 

12.  Describe  the  preparation  of  water  gas.     Why  is  it  so  called? 

13.  How  is  the  composition  of  water  gas  different  from  that  of 
coal  gas? 

14.  Write  the  equation  showing  the  effect  of  the  hot  coke  on  the 
steam. 

15.  What  is  meant  by  "live"  steam? 


CHAPTER  XV 

FLAME 

Outline — 

Definition  of  Flame 
Chemical  Reaction  in  a  Flame 
Structure  of  Flames 
The  Bunsen  Burner 
Applications  in  the  Home 
The  Oxyhydrogen  Blowpipe 
The  Blast  Lamp 

1.  What  is  a  Flame? — Briefly  stated,  a  flame  is  usu- 
ally said  to  be  a  burning  gas.  It  is  the  phenomenon 
which  accompanies  the  rapid  union  of  two  gases,  produc- 
ing heat  and  usually  light  also.  At  first  thought  this 
might  not  seem  to  be  always  true.  In  the  case  of  a 
burning  gas  jet  there  could  be  no  question  about  it.  The 
gas,  being  heated  to  the  kindling  temperature,  begins  to 
combine  with  the  oxygen  of  the  air;  this  chemical  union 
is  productive  of  heat  and  a  temperature  above  that  nec- 
essary for  the  kindling  of  the  gas  is  constantly  maintained. 
With  a  candle  it  is  equally  true.  The  wick  is  filled 
with  wax.  When  a  burning  match  is  applied  to  it,  first 
the  wax  is  melted,  then  it  begins  to  vaporize  and  the 
gas  thus  formed  is  ignited.  Thereafter,  the  heat  of  the 
chemical  union  is  such  as  to  vaporize  continuously  the 
paraffin  with  a  steady  flow  of  gas.  By  quickly  blowing 
out  the  flame  of  the  candle,  the  paraffin  vapors  may 
be  seen  floating  upward  and  may  easily  be  ignited  with- 
out touching  the  wick.  When  this  is  done  the  flame 
rapidly  passes  down  the  stream  of  gas  to  the  wick.  Ex- 
actly the  same  thing  is  true  of  the  kerosene  or  alcohol 
lamp.  Likewise,  when  wood  is  burning  the  heat  of 

189 


190  APPLIED    CHEMISTRY 

combustion  decomposes  the  cellulose  and  other  com- 
pounds present,  converting  much  of  them  into  gaseous 
form.  These  escape  in  tiny  streams  here  and  there  and 
combining  with  the  oxygen  produce  flames.  It  is  the 
same  with  soft  coal.  The  oil  contained,  by  means  of  the 
kindling  used,  is  first  partially  volatilized;  later,  by  the 
heat  of  combustion  not  only  does  volatilization  continue 
but  also  decomposition  of  the  vapors  into  hydrocarbon 
gases,  all  of  which  are  combustible.  Charcoal,  coke  and 
anthracite  coal  contain  little  or  no  volatile  matter; 
hence,  they  burn  without  flame.  It  is  true  that  often 
light  blue  lambent  flames  may  be  seen  above  the  surface 
of  such  fires,  but  these  are  due  to  the  carbon  monoxide, 
produced  in  the  interior  of  the  burning  mass  through 
the  interaction  of  the  carbon  dioxide  and  red-hot  carbon. 
This  has  been  explained  elsewhere.  It  must  be  con- 
cluded, therefore,  that  whenever  there  is  flame,  there  is 
a  gas  present. 

2.  The  Chemical  Action. — Combustion  is  sometimes 
spoken  of  as  the  rapid  union  of  oxygen  and  some  other 
substance.  This  is  a  narrow  view.  A  flame  may  accom- 
pany the  union  of  a  variety  of  substances,  and  in  each 
particular  case,  one  of  the  substances  is  as  essential  as 
the  other.  For  example,  an  ignited  jet  of  hydrogen, 
thrust  into  a  bottle  of  chlorine,  continues  to  burn  as  vig- 
orously as  in  the  air.  Likewise,  if  an  inverted  bottle  of 
hydrogen  be  ignited  at  the  mouth  and  a  jet  of  chlorine  be 
introduced  through  the  flame  into  the  bottle,  the  chlorine 
will  be  seen  to  burn.  In  this  case  combustion  is  the  rapid 
union  of  the  hydrogen  and  chlorine,  and  it  makes  little 
difference  which  is  introduced  into  the  other;  one  is  just 
as  essential  as  the  other.  In  the  same  way  a  stream  of 
air,  or  oxygen,  passed  through  the  flame  into  the  bottle 
of  hydrogen  continues  to  burn  just  as  well  as  the  jet  of 


FLAME  191 

hydrogen  does  in  the  air.  This  is  illustrated  by  a  com- 
mon, simple  experiment.  The  smaller  tube  in  Fig.  42, 
marked  ' '  gas, ' '  is  attached  to  the  gas  supply.  The  larger, 
short  tube  is  open  to  the  air.  When  the  gas  has  been  flow- 
ing sufficiently  long  to  expel  all  the  air  a  small  flame 
brought  to  the  upper  end  of  the  "air"  tube  will  apparently 
ignite  the  air  current  and  it  will  continue  to  burn.  Here 
the  combustion  is  the  union  of  the  gas  and  oxygen  and 
the  flame  occurs  at  the  place  where  this  union  is  going 
on. 


Fig.   42. — "Burning"   air. 

3.  Structure  of  a  Flame. — The  ordinary  flame  of 
which  that  given  by  a  candle  is  typical  consists  of  three 
portions,  or  concentric  cones.  A  few  simple  experiments 
readily  enable  one  to  determine  the  condition  of  each 
of  these  portions.  A  pine  splint  held  across  the  flame 
of  a  large  candle,  or  more  conveniently,  a  small  Bunsen 
burner  flame,  will  be  scorched  in  two  places,  at  the 
points  where  it  intersects  with  the  circumference  of  the 
flame.  If  a  sheet  of  paper  be  pressed  down  upon  a 
small  Bunsen  flame,  or  better,  if  the  burner  be  inverted 
and  held  close  to  the  paper  lying  on  the  table,  it  will 
be  scorched  in  a  circle,  agreeing  with  the  circumfer- 
ence of  the  flame.  These  would  indicate  that  the  burn- 


192 


APPLIED    CHEMISTRY 


ing-  portion  of  the  flame  is  at  the  outer  edge.  To  show 
this  more  strongly,  a  match  may  be  thrust  through  the 
outer  zone  and  held  until  the  wood  begins  to  burn  at 
the  circumference  of  the  flame  without  the  more  com- 
bustible material  of  the  head  of  the  match  being  ignited 
at  all.  This  may  be  varied  by  turning  off  the  gas  and 
suspending  a  match  in  the  burner  by  means  of  a  pin 
thrust  through  the  wood  a  half  inch  or  so  from  the  head. 
If  now  the  gas  is  turned  on  and  ignited  at  some  dis- 
tance above  the  tip,  it  will  burn  as  usual  while  the  match 
remains  unaffected  at  the  center.  These  experiments 


I 


Fig.   43. — Match   suspended  within  burning  gas   jet. 

show  that  there  is  no  heat  in  this  innermost  cone;  lastly, 
a  small  tube  inserted  into  this  section  and  held  at  an  an- 
gle, may  be  lit  at  the  upper  end.  This  shows  that  this 
portion  contains  unburned  gas.  The  same  experiments 
may  be  carried  out  with  a  large  candle.  (See  Fig.  44.) 
Inspection  of  a  Bunsen  flame  Avith  the  openings  near 
the  bottom  closed  or  of  the  candle  flame  shows  that  the 
middle  cone  is  yellow.  Around  this  is  an  outer  blue 
cone,  very  thin  at  the  base,  much  larger  in  the  upper 
part.  A  cold  dish  held  against  the  yellow  portion  is 


FLAME  193 

soon  covered  with  soot  which  we  know  is  a  deposit  of 
carbon.  It  is  the  myriads  of  carbon  particles  floating 
in  this  zone  and  heated  to  incandescence,  that  is  to  a 
temperature  at  which  they  will  glow,  which  give  the 
light.  It  may  be  concluded  then  that  this  middle  cone 
consists  of  gas  undergoing  combustion  but  not  com- 
pleted and  contains  much  incandescent  carbon.  The 
outer  cone  gives  little  or  no  light.  In  the  daytime  it 
looks  much  smaller  than  it  really  is.  A  pine  splint  ap- 


Fig.   44. — Burning   gas   drawn    from   center    of   candle   flame. 

proached  slowly  from  above  or  from  the  side  ignites 
long  before  it  touches  any  visible  flame.  This  is  evi- 
dently the  hot  portion  and  is  the  zone  of  complete  or 
perfect  combustion:  In  it  the  carbon  is  burned  to  carbon 
dioxide  and  the  hydrogen  to  vapor.  Obviously,  if  heat 
is,  desired  as  in  softening  a  glass  rod,  it  will  be  secured 
in  the  upper,  nearly  invisible,  blue  portion  of  the  flame. 
If  reducing  action  is  wanted,  since  red-hot  carbon  has 


194  APPLIED    CHEMISTRY 

such  power,  it  will  be  had  in  the  yellow  cone.  A  penny 
held  in  the  tip  of  the  flame  becomes  black  from  a  coating 
of  copper  oxide ;  held  in  the  yellow  portion  it  becomes 
bright  again  because  the  hot  carbon  removes  the  oxygen 
from  the  film  of  oxide. 

4.  The  Bunsen  Burner.— There  are  several  types  of 
this  burner  found  in  laboratories.     In  all  of  them  the 
gas   enters   through   a   very   small   opening   somewhere 
near  the  bottom,  and  all  have  some  arrangement  for 
introducing  considerable  air  somewhere  near  where  the 
gas  enters,  so  that  the  two  become  mixed  before  leav- 
ing the  tube.     The  result  is  that  if  properly  adjusted 
there  are  only  two  portions  to  such  a  flame.     The  lu- 
minous part  has  disappeared,  while  the  outer  cone  is 
much  enlarged.     There  is  thus  obtained  a  hotter  flame 
than  is  possible  otherwise.    By  opening  and  closing  the 
air  vents  at  the  bottom  it  will  be  seen  that  the  flame  is 
much  shorter  when  the  air  is  on  than  otherwise;  hence 
all  the  heat  of  the  combustion  is  concentrated  within  a 
shorter  portion  than  when  the  air  is  not  entering.    Some- 
times, in  such  burners,  if  the  gas  pressure  is  low,  the 
burner  "strikes  back"  and  continues  to  burn  near  the 
base.     In  this  case  the  rate  of  combustion  or  speed  of 
propagation  of  the  flame  has  been  more  rapid  than  the 
flow  of  gas,  and  the  flame  is  passed  down  the  pipe  to 
the  point  of  exit  of  the  gas.     Owing  to  the  lack  of  air 
needed   for   perfect    combustion,    acetylene    and    other 
offensive  gases  are  often  produced  in  such  cases  and  the 
difficulty  should  be  speedily  remedied.    Usually  by  turn- 
ing off  the  gas  and  lessening  the  air  supply  the  burner 
may  be  relit  successfully. 

5.  Applications  in  the  Home. — Every  gas  stove  used 
for  cooking  and,  as  a  rule,  for  heating  as  well,  employs 
the  principle  of  the  Bunsen  burner.     There  is  some  de- 


FLAME  195 

vice  for  admitting  a  supply  of  air  and  mixing  it  with 
the  gas  before  it  reaches  the  burner  where  it  is  to  be 
consumed.  If  properly  adjusted,  the  flame  will  be  blue 
and  relatively  hot.  A  yellow  flame  indicates  that  not 
sufficient  air  is  being  provided ;  hence  results  will  be 
slow  and  unsatisfactory.  Sometimes  the  burners  on  a 
stove,  especially  the  oven,  may  strike  back  and  burn  at 
the  point  of  admixture  of  the  gas  and  air.  This  is  espe- 
cially apt  to  occur  after  the  oven  has  been  burning  for 
some  time  and  the  pipes  have  become  hot,  The  cause  is 
the  same  as  in  the  case  of  the  Bunsen  burner.  The  rem- 
edy is  to  turn  off  the  gas,  decrease  the  air  supply  and 
relight.  With  poor  gas  pressure  there  is  sometimes  no 
remedy  except  to  allow  the  pipes  to  cool. 

6.  The  Oxyhydrogen  Blowpipe. — This  burner  has  been 
described  elsewhere,  under  hydrogen.     If  the  flame  ob- 
tained by  this  torch  or  with  acetylene  be  examined,  it 
will  be   seen  to   consist   of  only  two   portions — a  very 
small  inner  cone  and  a  nearly  invisible  outer  one.     The 
gases  used  are  so  proportioned  and  so  thoroughly  mixed 
before  they  issue  from  the  tip  that  the  combustion  is 
perfect  throughout  nearly  the  entire  mass.     Further,  it 
will  be  seen  that  the  flame  is  relatively  a  small  one.    The 
result  is  a  flame  of  very  great  intensity. 

7.  The   Blast  Lamp. — The   construction   of  the   blast 
lamp  is  not  essentially  different  from  that  of  the  oxy- 
hydrogen  torch.     The  inner  pipe  is  attached  either  to  a 
foot  bellows  or  to  a  tank  of  compressed  air,  while  the 
outer  connects  with  the  gas  supply.     Before  the  air  is 
turned  on,  the  gas  burns  with  a- large,  flickering,  yellow 
flame,  with  low  temperature.     With  the  air,  the  flame 
decreases   greatly   in   size,   loses   its   yellow   portion,   be- 
comes blue  and  almost  invisible,  and  has  a  high  tern- 


196  APPLIED    CHEMISTRY 

perature.  The  admixture  of  the  air  in  the  tube  enables 
the  entire  amount  of  the  gas  to  be  consumed  within  a 
small  space,  so  that  the  heat  is  all  concentrated  therein. 

Exercises  for  Eeview 

1.  What  is  a  flame?     Show  that  what  you  say  is  true  of  the  can- 
dle and  of  a  kerosene  lamp. 

2.  Give  some  experimental  proof  that  a  stream  of  gas  is  being 
formed  in  the  candle  wick. 

3.  What  is  the  explanation  of  the  flame  above  a  hard  coal  fire? 

4.  Explain  combustion  in  a  broad  sense.     Show  how  air  may  be 
"burned." 

5.  Of  how  many  portions  does  an  ordinary  flame  consist? 

6.  Give   some   simple   experiments  to   show   something  as  to  the 
character  of  the  innermost  part  of  a  flame. 

7.  What   does  the   middle   cone   contain?     What   proof   can  you 
give? 

8.  What  is  the  character  of  the  outer  cone?     How  do  you  think 
it  would  appear  different  at  night  from  in  the  daytime? 

9.  What  is  meant  by  incandescence? 

10.  Describe  the  Bunsen  burner  as  found  on  your  desk. 

11.  What  effect  does  the  construction  of  the  Bunsen  burner  have 
on  the  structure  and  character  of  the  flame? 

12.  Why  is  the  flame  shorter  when  the  air  is  on -at  the  bottom? 

13.  Explain  why  a  burner  strikes  back  and  give  the  remedy. 

14.  What  applications  of  the  Bunsen  burner  are  found  in  most 
city  homes? 

15.  What  is  the  trouble  when  a  gas  flame  on  a  cook  stove  burns 
yellow?     How  can  it  be  remedied? 

16.  Explain  why  the  oxyhydrogen  flame  is  so  intense  in  heat. 

17.  Describe   the   construction   of   the   blast   lamp.     Why   is  the 
flame  so  large  before  the  air  is  turned  on? 


CHAPTER  XVI 

METHODS   OF  LIGHTING 
Outline — 

Primitive  Methods  of  Lighting 
Kerosene  Lamps 
Gas  Illumination 
Incandescent  Electric  Lights 
The  Wclsbach  System 
Tungsten  Electric  Lamps 
The  Lime  Light 
Arc  Lights 

1.  Primitive  Methods  of  Lighting. — When  man  first 
began  to  use  artificial  light  is  not  known.     Probably  in 
some  localities,  at  first  it  was  the  pine  knot  full  of  resin ; 
in  others,  a  bowl  of  oil  into  which  was  dipped  a  twisted 
rag  or  something  Avhich  served  as  a  wick.    Miners,  even 
now,  often  carry  upon  their  caps  a  lamp  containing  a 
thick  oil  with  a  wick  enclosed  in  a  tube.     Such  lights 
are  necessarily  poor,  more  or  less  unsteady,  and  produc- 
tive of  smoke.     The  candle  was  an  improvement  upon 
the  old,  open  oil  lamp.     At  first,  tallow  was  used  and 
later  the  oil  of  the  sperm  whale.     Sometimes,  even  now, 
for  hard  candles,  tallow  is  treated  with  an  acid  to  pre- 
cipitate the   stearic   acid  from  the   stearin  and   this   is 
melted  and  molded  into  shape.     Those  most  commonly 
used,  however,  are  made  of  paraffin,  obtained  from  pe- 
troleum.    The  light  obtained  is  due,  as  explained  in  a 
preceding  chapter,  to  the  presence  of  the  incandescent 
carbon  particles  in  the  flame. 

2.  The  Kerosene  Lamp. — A  decided  advancement  was 
made  in  lighting  when  the  kerosene  lamp  was  invented. 
The  principle  is  not  different  from  that  of  the  candle. 

197 


198 


APPLIED    CHEMISTRY 


By  capillarity  the  oil  is  drawn  up  through  the  wick 
and  burned  at  the  top.  The  chimney  is  the  source  of 
the  increased  light.  By  means  of  the  perforations  in 
the  support  for  the  chimney  at  the  bottom  a  draft  is  se- 
cured so  that  the  combustion  is  more  rapid,  the  carbon 
particles  in  the  incandescent  zone  reach  a  higher  tem- 
perature and,  therefore,  give  more  light.  Moreover,  the 
flame  is  a  steady  one  and  produces  less  smoke.  In  ear- 
lier years  there  was  frequently  more  or  less  gasoline 


Fig.    45. — Determination   of   flash   point    of   an    oil. 

mixed  with  the  kerosene,  for  at  that  time  there  was  no 
demand  for  the  lighter  oil.  As  a  result,  explosions 
were  not  uncommon.  This  led  to  legislation  requiring 
all  merchantable  kerosene  to  be  inspected  and  possess 
a  certain  " flash  point."  This  means  the  temperature 
at  which  the  vapor  arising  from  it  will  ignite.  It  may 
be  shown  fairly  well  by  a  very  simple  method,  as  seen 
in  Fig.  45.  A  thermometer  is  supported  on  a  stand  at 
such  a  height  as  to  dip  within  some  gasoline  or  kerosene 
in  a  beaker.  A  piece  of  cardboard  with  an  opening 


METHODS    OF    LIGHTING  199 

cut  on  one  side  covers  the  beaker.  The  oil  is  then  slowly 
and  cautiously  heated  with  a  small  flame.  At  intervals, 
a  small  wax  taper,  lighted,  is  brought  to  the  opening  in 
the  cardboard.  The  temperature  at  which  the  vapor 
arising  catches  fire  or  " flashes"  through  the  space  above 
the  oil  is  called  the  flash  point.  At  the  present  time, 
since  gasoline  is  the  valuable  product  obtained  from  pe- 
troleum, kerosene  is  always  free  from  the  more  volatile 
oil  and  explosions  are  almost  unknown. 

3.  Gas  Illumination. — The  next  step  in  artificial  light- 
ing was  by  means  of  gas,  at  first  made  from  soft  coal. 
For  its  combustion  a  burner  was  used  closed  at  the  top 
by  a  little  cap  made  of  fire  clay  or  some  similar  non- 
combustible  material,  with  a  narrow  slit  for  the  escape 
of  the  gas.     When  ignited  a  thin,  fan-shaped  flame  was 
the  result.     The  light  produced  was  the  result  of  the 
incandescent  carbon  particles  as  in  other  cases  already 
studied. 

4.  Electric  Lights. — The  next  improvement  in  light- 
ing systems  was  that  of  the  incandescent  electric  bulb. 
It  had  long  been  known  that  a  wire  of  high  resistance 
carrying  an   electric   current   would   become   luminous. 
Attempts  were  made  with  platinum  and  other  metals  in 
electric  lamps,  but  none  of  them  gave  sufficient  light  to 
be  of  value.    Finally,  after  years  of  experimenting  with 
all  sorts  of  vegetable  fibers,  one  from  a  special  bamboo 
was  obtained  sufficiently  strong  to  be  used  in  a  lamp. 
Later,  these  carbon  filaments  were  obtained  by  carbon- 
izing threads  made  from  a  viscous  solution  of  cellulose, 
much  as  fiber  silk  is  now.     The  air  was  pumped  out  of 
the  bulb,  so  as  to  prevent  the  rapid  disintegration  or 
combustion   of  the   carbon  thread.     In   such   lamps,   it 
will  be  seen  that  the  light,  as  in  all  other  cases  already 
mentioned,  is  obtained  by  incandescent   carbon.     Natu- 


200  APPLIED    CHEMISTRY 

rally,  they  were  called  incandescent  lights.  The  con- 
venience of  turning  on  or  off  such  lamps  was  great,  and 
the  candle  power  was  higher,  but  the  quality  of  the 
light  otherwise  was  not  essentially  different  from  the 
gas-light. 

5.  The  Welsbach  Mantle.— Two  things  led  to  the  in- 
vention of  the  gas  mantle.     One  was  the  discovery  of 
natural  gas,  and  the  desire  to  use  it  for  illuminating 
purposes.    As  it  is  low  in  carbon  content,  when  burned 
in  the  old-fashioned  slit-top  burner,  it  gives  very  little 
light,  not  sufficient  to  be  of  value.     The  other  reason 
was  the  greater  convenience  offered  by  electricity  with 
the   resulting   strong    competition,    threatening   to    dis- 
place gas  entirely.     At  such  a  time  the  mantle  was  in- 
vented by  a  man  named  Welsbach.    It  is  made  by  spray- 
ing upon  a  little  hood  made  from  long  fiber  mercerized 
cotton,  a  mixture  of  thorium  and   cerium  nitrates,   99 
parts  to  1.     The  burner  upon  which  it  is  used  is  almost 
identically  that  invented  by  Bunsen.     For  use  the, man- 
tle is  hung  over  the  burner  and  ignited.     The  cotton 
burns  off,  while  the  two  nitrates  by  the  heat  are  con- 
verted into  oxides.     Now,  when  the  gas  is  ignited,  the 
burner  gives  a  short,  hot  flame  which  heats  the  two  ox- 
ides into  incandescence  just  as  the  oxyhydrogen  flame 
does  the  stick  of  lime,  which  is  calcium  oxide.     At  the 
temperature  obtained,  the  oxides  give  a  beautiful,  white 
light,  six  or  eight  times  as  strong  as  the  old  style  tip. 
Natural  gas  can  be  used  in  this  burner  as  well  as  arti- 
ficial.    The  quality  of  the  light  is  greatly  superior  to 
that  of  the  incandescent  carbon  electric,  and  not  essen- 
tially different  in  candle  power. 

6.  Acetylene. — This  gas  has  been  mentioned  elsewhere 
although  it  is  used  more  for  illumination  than  for  cook- 
ing purposes.     It  must  be  burned  in  a  special  tip  and 
cannot  be  used  with  the  Welsbach  mantle.     It  gives  a 


METHODS    OF    LIGHTING  201 

beautiful  white  light,  but  as  the  gas  must  be  manufac- 
tured in  the  place  where  it  is  be  used,  it  is  not  adapted 
to  the  wants  of  a  city.  Its  field  must  always  be  the 
suburban  or  country  home. 

7.  The  Tungsten  Lamp.— The  quality  of  the  light  af- 
forded by  the  Welsbach  gas  system  stimulated  the  elec- 
tric companies  to  discover  some  filament  which  would 
give  a  white  light  comparable  with  gas.     Several  sub- 
stances other  than  carbon  have  been  tried,  but  at  the 
present  time  tungsten  is  regarded  as  the  most  desira- 
ble.    When  first  adopted  such  lamps  were  very  fragile, 
owing   to   the   brittleness   of  the   filament,   and   gained 
slowly  in  favor.     They  have  been  perfected  now,  how- 
ever, so  that  they  are  practically  as  durable  as  the  car- 
bon filaments.     They  give  a  brilliant  white  light,  and 
consume  much  less  current  for  the  saine  candle  power 
than   the    old   style   lamp.      An   improved   form    of   the 
tungsten   lamp   now  has   the   bulb   filled   with   nitrogen 
instead  of  the  usual  vacuum.     They  are  more  durable 
and  at  the  same  time  give  a  better  light,     Without  acci- 
dent a  tungsten  lamp  should  give  about  1,000  hours  of 
actual  service. 

8.  The  Calcium  or  Lime  Light. — This  has  been  men- 
tioned elsewhere  as  the  Drummond  light.    The  principle 
is  not  different  from  that  seen  in  all  other  cases  and  is 
due  to  the  incandescence  of  a  solid.     In  this  case  it  is 
the  stick  of  lime,  calcium  oxide,  upon  which  an  intensely 
hot  flame  is  allowed  to  strike.    Its  brilliance  rivals  that 
of  the   electric  arc.     Its  use  has  been  mentioned  else- 
where. 

9.  Arc  Lights. — In  arc  lights  two  sticks  of  gas  carbon 
are  used  which  in  service  are  separated  from  each  other 
by  a  short  distance.    An  electric  current  of  high  voltage, 
in  spanning  the  gap,  does  so  not  in  a  straight  line,  but 
curved  like  the  arc  of  a  circle.     The  positive  carbon 


202  APPLIED    CHEMISTRY 

is  worn  away  and  the  particles,  white  hot,  are  carried 
across  the  gap  and  in  part  deposited  upon  the  negative 
carbon.  It  is  these  white-hot  particles  which  produce  the 
dazzling  light.  At  first  the  two  carbons  were  used  in  large 
globes  entirely  exposed  to  the  air.  As  a  result  they 
were  burned  away  rapidly,  so  that  a  great  deal  of  time 
was  needed  in  replacing  them,  in  addition  to  the  ex- 
pense of  the  carbons  themselves.  At  the  present  time 
they  are  enclosed  in  small  globes. .  These  are  not  air- 
tight, but  through  combustion  they  are  soon  filled  with 
carbon  dioxide  so  that  the  subsequent  disintegration  is 
slow.  Arc  lights  are  used  mainly  for  lighting  of  streets, 
and  spot  lights  for  stage  effects. 

Exercises  for  Review 

1.  Name  some  of  the  different  kinds  of  candles  made.     How  is 
light  produced  in  a  candle? 

2.  Explain  why  the  kerosene   lamp  gives  better  light  than  the 
candle.     Why  were  they  explosive  at  first? 

3.  What  is  meant  by  the  flash  point  of  an  oil?     How  may  it  be 
obtained  approximately? 

4.  Describe  the  tip  used  in  the  original  gas  lamp.     What  pro- 
duces the  light  in  such  a  flame? 

5.  Describe   the   incandescent   carbon  lamp.     How   are  the   car- 
bon filaments  made  now?     How  originally  obtained? 

6.  What  objection  to  the  carbon  electric?     What  advantage  has 
it  over 'gas? 

7.  Describe  the  Welsbach  mantle  and  burner.    What  are  its  ad- 
vantages? 

8.  What  kind  of  a  tip  is  used  with  acetylene?    Where  are  acety- 
lene lights  seen  frequently?     To  what  kind  of  lighting  is  it  essen- 
tially suited? 

9.  How   is   the   tungsten    lamp   different   from   the    old    carbon? 
What  objection  was  there  to  them  at  first? 

10.  In  working  about  a  tungsten  lamp,  as  in  dusting  or  cleaning, 
what  can  be  done  to  render  them  still  less  liable  to  break? 

11.  How  is  the  calcium  light  obtained?     For  what  is  it  used? 

12.  Why  are  arc  lights  so  named?    Where  used?    What  produces 
the  light?     Where  are  the  carbons  obtained  whi^h  are  used  in  the 
arc  light? 


CHAPTER  XVII 

SOME  ORGANIC  COMPOUNDS 
Outline — 

Hydrocarbons 

(a)   Methane 

(&)   Gasoline  and  Kerosene 

(c)   Derivatives  of  Methane 
The  Alcohols 

(«)   AA^ood  Alcohol 

(&)    Grain  Alcohol 
Organic  Acids 

(a)  Formic 

(b)  Acetic 
Aldehydes 

Formalin 
Ethers 

1.  Hydrocarbons. — It  has  been  stated  elsewhere  that 
the  study  of  carbon  compounds  constitutes  a  separate 
branch  of  chemistry,  known  as  "Organic  Chemistry." 
The  compounds  were  originally  so  named  because,  as 
far  as  observed,  they  were  produced  only  by  organized 
life  forces.  This  is  known  IIOAV  not  to  be  true.  From 
their  very  great  practical  value  in  everyday  life  with 
some  of  these  compounds  it  is  important  that  the  student 
should  become  familiarized.  Among  the  simplest  of 
such  compounds  are  the  hydrocarbons,  which  contain  as 
the  name  indicates  only  carbon  and  hydrogen.  In  a  pre- 
ceding chapter  marsh  gas  has  been  mentioned,  as  have 
also  gasoline,  kerosene  and  various  other  oils  derived  from 
petroleum.  All  these  are  really  paraffins  and  belong  to 

203 


204  APPLIED    CHEMISTRY 

a  regular  series  in  which  over  sixty  have  been  prepared. 
The  first  six  are  here  given, 

Methane,  CH4, 
Ethane,  C2H(;, 
Propane,  C3H8, 
Butane,  C4H10, 
Pentane,   C5H12, 
Hexane,  C0H14. 

The  subsequent  members  of  the  series  receive  their  names 
from  the  Greek  numerals  as  the  last  two  given  above,  the 
first  part  of  the  name  indicating  the  number  of  carbon 
atoms.  Examination  of  the  formulas  shows  that  the  dif- 
ference between  any  two  successive  members  is  CH2; 
hence,  it  becomes  a  simple  matter  to  write  formulas  for 
the  entire  series.  Further  it  will  be  observed  that  the 
hydrogen  is  always  twice  the  carbon  plus  two.  The  gen- 
eral formula  for  any  paraffin,  therefore,  is  CnH2n  +  2  in 
which  n  represents  the  number  of  the  carbon  atoms.  Of 
the  more  than  sixty  paraffins  known,  the  first  five  are 
gases,  then  follow  a  very  considerable  number  of  liquids, 
and  above  these  are  the  solids  with  which  all  are  familiar 
in  the  white  wax  of  commerce. 

2.  Methane. — This  is  commonly  known  as  marsh  gas, 
because  of  the  fact  that  it  is  produced  in  swamps  and 
stagnant  creek  beds  where  decomposition  of  leaves  and 
other  organic  matter  is  taking  place.  It  occurs  in  coal 
mines,  and  is  known  by  the  miners  as  fire  damp,  the 
word  damp  being  their  name  for  gas.  It  is  so  called  be- 
cause of  its  dangerous,  explosive  character.  It  is  this 
gas  which  causes  practicallly  all  the  explosions  in  coal 
mines.  As  in  such  cases  the  combustion  is  more  or  less 
imperfect  from  the  limited  supply  of  air,  much  carbon 
monoxide  usually  exists  in  the  mine  following  the  explo- 


SOME   ORGANIC    COMPOUNDS  205 

sion.  This  has  been  mentioned  before  as  the  fatal  black 
damp.  It  has  been  mentioned,  also,  that  methane  is  the 
chief  constituent  of  natural  gas,  is  more  than  40  per  cent 
of  coal  gas,  as  well  as  a  very  considerable  part  of  water 
gas.  It  is  colorless,  has  a  density  only  eight  times  that 
of  hydrogen  or  little  more  than  half  that  of  the  air,  is 
odorless,  and  burns  with  an  almost  invisible  blue  flame. 
On  account  of  its  having  no  odor  its  presence  in  mines 
cannot  be  detected  by  the  senses.  For  protection  against 
it,  more  than  a  century  ago,  Sir  Humphrey  Davy  in- 
vented a  safety  lamp  which  consists  really  of  very  little 
more  than  a  chimney  of  fine  wire  gauze,  surrounding  the 
flame,  like  the  chimney  on  a  lantern.  All  it  does  is  to 
prevent  the  gas  on  the  outside  from  becoming  heated 
to  its  kindling  temperature.  This  will  be  understood  if 
a  wire  gauze  be  held  above  a  burning  Bunsen  flame.  Ap- 
parently, it  is  possible  by  means  of  the  gauze  to  push  the 
flame  down.  Really,  however,  what  it  does  is  to  conduct 
the  heat  away  from  the  gas  and  dissipate  it  so  that  the 
gas  in  passing  through  is  cooled  below  its  kindling  point. 
That  this  is  so  may  be  shown  by  bringing  a  flame  to  the 
current  of  the  gas  above  the  gauze.  It  is  quickly  ignited 
and  goes  on  burning. 

3.  Gasoline  and  Kerosene. — Gasoline  consists  mainly 
of  the  sixth,  seventh  and  eighth  of  the  paraffin  series, 
hence  is  a  mixture.  Benzine  and  the  other  light  oils 
mentioned  as  belonging  to  the  gasoline  fraction  obtained 
from  petroleum  below  150°  C.  may  be  separated  from 
each  other  by  taking  smaller  fractions.  To  illustrate, 
a  sample  of  gasoline  may  begin  to  boil  at  about  75°  C.: 
the  petroleum  ether  comes  off  first  and  because  it  has  a 
very  low  boiling  point  it  is  soon  all  distilled  over.  The 
receiving  flask  will  then  be  removed  and  another  at- 
tached for  the  next  fraction.  Kerosene  consists  of  the 


206  APPLIED    CHEMISTRY 

eight  paraffins  just  above  the  gasoline  series.  Having 
seen  the  close  relation  of  the  various  oils  to  each  other 
in  the  paraffin  series,  it  is  less  difficult  to  understand 
how  by  "cracking"  it  might  be  possible  to  convert  the 
higher  members  into  the  lower,  since  a  single  molecule 
of  the  heavy  oils  might  make  two  or  more  of  the  lighter 
ones. 

4.  Derivatives  of  Methane. — A  derivative  as  the  term 
is  used  here  is  a   compound  obtained  by   substituting 
an  atom  or  atoms  of  some  element  or  some  radical  group' 
for  one   or  more   of  the  hydrogen  atoms  in  the   com- 
pound.    One  of  the  most  simple  as  well  as  familiar  de- 
rivatives of  methane  is  chloroform,  CHC13,  obtained  in- 
directly  by   substituting   three    atoms   of    chlorine    for 
three    of   the   hydrogen   in   methane.      lodoform,    men- 
tioned  elsewhere,   is    a   corresponding   derivative    with 
the  formula,  CHL.     Carbon  tetrachloride,  mentioned  as 
a  good  fire  extinguisher,  is  also  a  derivative  in  which  all 
the  hydrogen  in  methane  has  been  replaced  by  chlorine. 
Chloroform  is  a  colorless,  oily  liquid  of  rather  pleasant 
odor  and  not  inflammable.     Its  use  as  an  anesthetic  is 
familiar.     It  has  the  advantage  over  ether  that  it  may 
be  used  near  an  open  flame  without  danger. 

5.  The    Alcohols,— There    are    two,    familiar    to    all, 
methyl,  or  wood  alcohol,  and  ethyl  or  grain  alcohol.    They 
are  derivatives  of  the  first  two  paraffins:  thus,  CH4  -» 
CH3OH,  and  C2H6  ->  C2H5OH,  in  both  of  which  a  hy- 
droxyl  group  has  been  substituted  for  a  hydrogen  atom. 
Each  of  the  paraffins  has  a  corresponding  alcohol,  the 
higher  ones  in  the  series  being  white  crystalline  solids. 
Wood  alcohol  is  obtained  by  the  destructive  distillation 
of  wood  in  making  charcoal.     It  is  a  colorless  liquid,  if 
pure,  has  a  somewhat  unpleasant  odor,  is  very  poison- 
ous,  inflammable   and   an    excellent   solvent   for   many 


SOME   ORGANIC    COMPOUNDS  207 

things.  Because  of  this  last  property  it  has  many  uses 
as  in  making  shellac,  and  similar  preparations.  How- 
ever, denatured  alcohol,  being  much  cheaper,  is  fast  tak- 
ing the  place  of  the  wood  alcohol  in  many  cases.  It  is 
grain  alcohol,  adulterated  by  the  addition  of  about  10 
per  cent  of  methyl  or  wood  alcohol  or  some  other  liquid 
to  render  it  more  or  less  disagreeable  in  odor,  and  unfit 
for  medicines,  extracts  or  as  a  beverage.  Adulterated,  as 
mentioned,  it  is  often  called  methylated  spirits.  The  United 
States  government  has  specified  at  least  eight  formu- 
las for  denaturing  alcohol  to  meet  the  various  demands 
of  manufacturers.  It  now  has  very  extensive  uses.  It 
is  one  of  the  most  commonly  employed  substances  to 
prevent  the  freezing  of  the  water  in  radiators  of  motor 
cars  and  trucks.  Ethyl  alcohol  is  made  from  grains. 
These  are  kept  damp  and  warm  for  several  days  till 
sprouted.  During  this  time  a  ferment  called  diastase, 
present  in  the  seed  and  provided  by  nature  to  convert 
the  insoluble  starch  present  into  soluble  form,  so  that  the 
embryo  plant  and  rootlets  can  use  it,  has  changed  the 
starch  into  a  form  of  sugar.  At  the  proper  stage,  learned 
by  experience,  the  grain  is  heated  to  stop  the  process;  it 
is  then  ground,  yeast  is  added  and  fermentation  begins 
whereby  the  sugar  into  which  the  starch  was  converted 
changes  into  alcohol  and  carbon  dioxide.  Thus, 

CfiII120(;  -•»  2C2H5OH  +  2C02. 

When  the  fermentation  is  completed  the  alcohol  is  dis- 
tilled out  and  put  upon  the  market  about  95  per  cent 
strength.  If  absolute  alcohol  is  desired  it  may  be  ob- 
tained by  treating  the  commercial  variety  with  lime  or 
anhydrous  copper  sulphate  and  distilling  carefully. 
Grain  alcohol  is  a  colorless  liquid,  of  pleasant  odor,  boil- 


208  APPLIED   CHEMISTRY 

ing  point  of  78°  C.,  and  almost  as  poisonous  as  methyl. 
It  is  used  in  preparing  many  medicines  as  a  solvent  or 
preservative,  in  extracts  for  domestic  or  other  purposes, 
and  in  a  great  variety  of  other  ways. 

6.  Organic  Acids. — From  each  of  the  alcohols,  by  oxi- 
dation, an  acid  may  be  derived.  Thus,  if  two  of  the  hy- 
drogens in  an  alcohol  are  removed  and  an  oxygen  atom 
substituted  for  them,  an  acid  is  obtained.  Methyl  al- 
cohol thus  gives  formic  acid,  HCOOH.  The  equations 
for  the  first  two  are 

CH3OH  +  02  -»  HCOOH +  H20, 
C2HBOH  +  02  -»  CH3COOH  +  H20. 

Like  the  paraffins  and  the  alcohols,  the  acids  differ  by 
CH2,  so  that  the  entire  series  is  easily  written.  These 
two  acids  might  be  given  thus,  H2C02  and  H4C202 ;  but 
they  are  usually  presented,  as  above,  to  indicate  the 
structure  of  the  molecule,  and  this  is  decidedly  pref- 
erable. The  empirical  formula,  H4C202,  tells  nothing 
but  the  number  of  atomic  weights  of  each  element  pres- 
ent, from  which  may  be  calculated  the  percentage  com- 
position :  the  graphic  formula  indicates  that  three  hy- 
drogen atoms  are  attached  to  one  carbon  atom,  and 
that  the  two  oxygen  atoms  are  attached  to  the  other 
carbon  but  not  in  the  same  manner,  and  that  the  remain- 
ing hydrogen  atom  is  attached  to  the  second  oxygen. 
It  is  more  fully  shown  thus, 

H  0 

H-C-C-0-H. 

I 
H 

The  first  acid  has  little  commercial  value.  It  is  secreted 
by  some  ants  and  received  its  name  from  the  Latin  word 


SOME    ORGANIC    COMPOUNDS  209 

for  ant,  forma.  It  is  also  secreted  by  the  stinger  gland 
of  such  insects  as  the  wasp,  bee,  and  the  hornet,  when  ex- 
cited. The  pure  acid  is  a  colorless  liquid,  and  upon  the 
skin  causes  intense  pain  and  produces  blisters.  It  is  this 
acid  injected  hypodermically,  that  causes  the  pain  when 
stung  by  any  of  the  above  insects.  Acetic  acid  is  widely 
used  in  a  diluted  form,  2  to  5  per  cent,  as  vinegar.  Orig- 
inally, it  was  obtained  largely  from  apple  cider  through, 
first  alcoholic  fermentation,  when  the  cider  became  hard, 
and  then  subsequent  oxidation  by  means  of  another  spe- 
cies of  bacterium.  At  the  present  time  the  demands  are 
too  great  to  be  met  in  this  way.  Some  is  obtained  in  the 
distillation  of  wood  in  making  charcoal ;  some  in  the  fer- 
mentation of  fruit  juices  other  than  that  of  the  apple; 
but  most  comes  from  the  glucose  prepared  from  corn 
starch.  A  solution  of  the  glucose  is  passed  slowly  through 
tanks  or  barrels  filled  with  shavings,  previously  inoculated 
with  the  bacterium,  Mycoderma  aceti,  familiarly  known 
as  "mother  of  vinegar."  The  process  is  rapid  and  the 
vinegar  obtained  is  free  from  the  many  organic  impuri- 
ties of  the  old-time  product,  especially  the  decayed  pulp 
of  the  apple.  It  also  does  not  contain  the  vinegar  eel,  a 
tiny  white  worm,  which  frequently  may  be  seen  in  count- 
less numbers  in  cider  vinegar  if  examined  carefully. 
Pure  acetic  acid  is  a  colorless  liquid,  which  becomes  solid 
at  16.7°  C.  It  is  often  called  glacial  acetic  for  this  reason. 
7.  Aldehydes. — From  each  alcohol  in  the  series  a  cor- 
responding aldehyde  may  be  obtained.  This  is  done  by 
carrying  the  oxidation  only  far  enough  to  remove  two 
atoms  of  hydrogen  without  introducing  anything  in 
their  place.  This  leaves  them  unsaturated  compounds ; 
hence,  they  are  reducing  agents.  The  only  one  of  im- 
portance is  formaldehyde,  which  is  prepared  from  methyl 


210  APPLIED    CHEMISTRY 

alcohol.  All  the  aldehydes  obtain  their  names  from  the 
corresponding  acid,  hence,  the  name  in  this  case.  The 
preparation  from  methyl  alcohol  is  shown  by  the  equa- 
tion, 

2CH3OH  +  02  ->  2HCOH  +  2H20. 

Formic  aldehyde  is  a  gas  which  liquefies  at  -21°  C.  For 
use  it  is  dissolved  in  water  and  is  put  on  the  market 
under  the  name  of  formalin,  a  40  per  cent  solution.  From 
this  the  gas  is  constantly  escaping,  irritating  in  odor, 
affecting  both  the  nostrils  and  eyes.  It  is  strongly  germi- 
cidal  and  is  used  extensively  for  disinfecting  purposes. 
This  is  easily  done  by  pouring  the  solution  upon  lime 
with  which  the  water  present  reacts  giving  sufficient  heat 
to  expel  the  gas  rapidly.  Since  it  is  a  hardener  of  tis- 
sues and  cheaper  than  alcohol  it  is  used  extensively  in 
preserving  various  zoological  and  botanical  specimens. 

8.  The  Ethers. — Corresponding  to  each  alcohol  is  an 
ether.  From  ethyl  alcohol  is  obtained  the  only  impor- 
tant one,  ethyl  ether.  Its  formula  is  (C2H5)20,  which 
indicates  that  it  is  an  oxide  of  the  ethyl  group.  It  is 
a  colorless  liquid,  of  sweet  pleasant  odor,  with  a  boiling 
point  below  the  temperature  of  the  human  body,  34.9° 
C.  It  is  very  inflammable,  and  an  excellent  solvent  of 
iodine,  as  also  of  oils  and  fats.  Inhaled  it  produces 
anesthesia.  It  is  regarded  as  a  safer  anesthetic  than 
chloroform,  but  cannot  be  used  near  an  open  flame. 

Exercises  for  Review 

1.  What  is  a  hydrocarbon1?     Name  six  with  formulas.     What  is 
an  organic  compound?     What  is  a  paraffin? 

2.  How  many  paraffins  are  known?     What  is  their  physical  con- 
dition? 

3.  Give  two  other  names  for  methane.   How  does  it  receive  these? 


SOME  ORGANIC  COMPOUNDS  211 

4.  Describe  the  safety  lamp  and  explain  how  it  works. 

5.  Of  what  does  gasoline  consist?     Into  what  several  oils   may 
it  be  separated?     What  is  this  process  called? 

6.  Name  two  halogen  derivatives  of  methane  and  use  of  each. 

7.  Name   two   alcohols  with   formulas.      To   what    class   of   com- 
pounds do  they  belong? 

8.  What  is  denatured  alcohol?     Give  some  uses  for  it. 

9.  What  is  methylated  spirits?     What  is  a  ferment? 

10.  How  is  grain  alcohol  made?     Give  uses. 

11.  Name   two   important    organic    acids.      From    what    are    they 
derived? 

12.  Where  does  each  of  these  occur  in  Nature? 

13.  How  is  the  commercial  supply  of  vinegar  obtained? 

14.  What    is    the    common    aldehyde?      Its    trade    name?      Uses 
for  it? 

15.  Give  formula  for  common  ether.     Of  what  use  is  it?     Com- 
pare with  chloroform. 


CHAPTER  XVIII 

ETHEREAL  SALTS,  OILS,  FATS,  SUGARS 

Outline- 
Esters  or  Ethereal  Salts 
Glycerol 

Esters  of  Glycerine 
Oleomargarine 
Compound  Lards 
Molecular  Structure  of  Fats 
The  Olenns 
Hydrogenation  of  Oils 
The  Carbohydrates 

(a)   Monosaccharides 

(5)   Disaccharides 

(c)   Polysaccharides 

1.  Esters. — It  will  be  remembered  that  a  base  is  a  hy- 
droxide. By  examining  the  formulas  of  the  alcohols  it 
will  be  seen  that  they  are  hydroxides.  They  are  organic 
bases  and,  combined  with  organic  acids,  they  produce 
what  are  called  ethereal  salts  or  esters.  The  first  term 
is  used  for  the  reason  that  many  of  them  have  pleasant 
odors  somewhat  resembling  ether.  The  word,  estert  is 
coined  from  the  other  two  and  has  no  meaning.  Several 
of  these  ethereal  salts  are  familiar  in  the  form  of  arti- 
ficial flavors  and  extracts,  such  as  banana,  pineapple,  and 
the  like.  They  may  be  had  of  the  grocers  and  are  found 
at  soda  fountains  in  some  of  the  syrups  used.  Thus, 
artificial  pineapple  is  ethyl  butyrate,  an  ester  of  grain 
alcohol  and  butyric  acid.  It  is  the  latter  that  gives  the 
strong,  disagreeable  taste  to  rancid  butter ;  apple  is  amyl 
valerate,  and  pear,  isoamyl  acetate.  The  ester  formed  by 
the  union  of  ethyl  alcohol  and  acetic  acid  has  a  pleasant 

212 


ETHEREAL  SALTS,   OILS,   FATS,   SUGARS  213 

fruity  odor  and  is  easily  made  in  the  laboratory.  It  is 
sometimes  used  as  a  test  for  the  presence  of  alcohol  in  a 
substance. 

2.  Glycerol. — This  compound  is  commonly  known  as 
glycerine.     Its  formula,  C3H5(OH)3,  shows  that  it  is  an 
organic  base  with  three  hydroxyl  groups;  it  is,  there- 
fore, an  alcohol.     It  is  obtained  as  a  by-product  of  the 
soap  industry.     In  home-made  soaps  it  is  not  separated 
out  and  in  some  special  varieties  of  factory-made,  such 
as  the  transparent  soaps.     But  the   great  demand  for 
glycerine  in  the  manufacture  of  explosives  as  described 
elsewhere  and  the  fact  that  it  adds  little  to  the  value 
of  the  soap  for  general  purposes,  has  led  to  its  careful 
separation.     Glycerine  is  a  sweet  syrupy  liquid,  nearly 
colorless  if  pure  and  very  soluble  in  water.     It  derives 
its  name  from  the  Greek  word  for  sweet  on  account  of 
its  taste.    Because  of  the  fact  that  it  is  hygroscopic,  when 
the  price  will  permit,  it  is  sometimes  used  in  small  quan- 
tities by  bakers  in  cakes  to  prevent  their  drying  out  so 
rapidly.    It  is  also  used  in  toilet  and  other  pharmaceuti- 
cal preparations,  but  the  greater  proportion  goes  to  the 
explosive  factories. 

3.  Esters  of  Glycerine. — It  is  the  salts  of  glycerine 
that  chiefly  interest  us,  for  they  are  the  common  fats 
and  oils  used  as  foods.    The  four  most  common  are 

Glyceryl   butyrate,   Butyrin,    C3H5(C3H7COO)S, 
Glyceryl  palmitate,  Palmitin,  G3H5(C15H31COO)3, 
Glyceryl   oleate,    Olein,    C3H5(C17H33COO)3, 
Glyceryl   stearate,   Stearin,    C3H-(C17H35COO).,. 

All  the  common  fats  and  oils  are  mixtures  of  three  or  all 
four  of  these.  Butter  contains  all  four ;  when  free  from 
water  the  butyrin  is  about  8  per  cent  of  the  whole.  It 
is  this  ester  that  gives  the  characteristic  pleasant  odor 


214  APPLIED    CHEMISTRY 

and  taste  to  butter.  Ordinarily,  there  is  in  butter  about 
12  to  14  per  cent  of  water,  with  some  casein  from  the 
milk.  Olive  oil  is  about  75  per  cent  olein.  Of  the  four 
fats  mentioned,  olein  has  the  lowest  melting  point,  being 
a  liquid  at  ordinary  temperatures,  and  stearin  has  the 
highest.  Any  fat,  therefore,  with  a  high  proportion  of 
olein  will  melt  easily  and  may  be  liquid  at  all  ordinary 
temperatures;  thus,  cotton-seed  oil  and  "mazola,"  an  oil 
made  from  corn  as  a  by-product  in  the  manufacture  of 
starch  and  glucose,  are  high  in  olein.  Common  lard  is 
about  60  per  cent  olein  and  melts  easily,  while  beef  fat  is 
high  in  stearin.  It  wTill  be  seen,  therefore,  that  the  vari- 
ous edible  fats,  whether  from  beef,  pork,  mutton,  or  of 
vegetable  origin,  are  very  similar  in  character.  If  the 
formulas  given  above  are  examined,  this  fact  is  even 
greatly  emphasized. 

4.  Oleomargarine. — The  demand  for  butter  is  far 
greater  than  the  supply.  This  has  led  to  the  preparation 
of  artificial  butters,  most  of  which  are  called  oleomar- 
garines. These  are  made  by  the  mixture  of  animal  and 
vegetable  oils,  which  are  much  cheaper  than  butter.  One 
formula,  used  by  one  of  the  large  packing  houses,  is 
given  below, 

Neutral  lard,  75  pounds 
Cottonseed  oil,  175  pounds 
Oleo  oil,  675  pounds 
Peanut  oil,  75  pounds 

These  are  put  into  60  gallons  of  milk  from  which  the 
cream  has  been  separated  and  churned.  The  purpose 
of  this  is  to  add  something  of  the  flavor  of  real  butter 
and  possibly  some  of  the  casein  of  the  milk.  The  fats 
are  removed  from  the  milk,  and  150  pounds  of  real  but- 
ter and  125  pounds  of  salt  are  added  and  the  whole 


ETHEREAL  SALTS,   OILS,    FATS,   SUGARS  215 

thoroughly  worked  together.  This  gives  a  total  weight 
of  solids  of  1,275  pounds.  In  the  churning  and  subse- 
quent working  of  the  mixture  considerable  water,  even 
as  much  as  12  per  cent  is  taken  up,  so  that  there  is 
finally  a  total  weight  of  between  1,400  and  1,500  pounds. 
In  this  variety  it  will  be  seen  the  butter  is  approximately 
10  per  cent  of  the  whole.  In  another  formula  used, 
the  real  butter  mixed  with  the  other  fats  may  run  as 
high  as  25  per  cent,  but  it  is  understood  that  this  par- 
ticular brand  is  not  put  on  the  general  market  but  sold 
entirely  to  special  customers.  Many  brands  contain  no 
butter  at  all.  At  the  present  time  oleos  in  which  cocoa- 
nut  oil  enters  to  a  very  considerable  extent  are  being 
manufactured  by  nearly  all  the  large  packing  compa- 
nies. The  advantage  claimed  for  these  butters  is  that  co- 
coanut  oil  contains  about  5  per  cent  of  butyrin ;  hence, 
they  much  more  nearly  approach  real  butter  in  com- 
position and  taste  than  do  those  with  a  higher  percent- 
age of  animal  oils.  For  years  after  their  introduction 
into  the  United  States  there  was  great  objection  made 
to  them  by  the  butter  producers  and  much  adverse  legis- 
lation resulted.  They  may  not  be  colored,  although  all 
creamery  butter  and  cheese  are ;  moreover,  oleos,  must 
pay  an  excise  tax,  which  somewhat  increases  their  cost  to 
the  general  public.  Nevertheless,  these  artificial  but- 
ters are  clean,  wholesome  articles  of  food,  nutritious,  and 
to  all  purposes,  of  practically  the  same  food  value  as 
the  real  article.  There  is  only  one  objection  and  that 
is  the  low  melting  point ;  thus  in  warm  weather  oleo- 
margarine is  more  difficult  to  keep  as  hard  as  is  desira- 
ble. In  spite  of  adverse  legislation  and  the  prejudice 
existing,  their  consumption  has  increased  wonderfully 
in  the  last  five  years.  Some  idea  of  this  may  be  obtained 
from  the  government  reports  concerning  the  importa- 


216  APPLIED    CHEMISTRY 

tion  of  cocoanut  and  other  vegetable  oils.  The  follow- 
ing table  gives  the  amounts  for  the  years  1914  and  1918, 
the  last  available  at  this  time. 


Oil 

1914 

1918 

Peanut  Oil 
Soy   Bean   Oil 
Cocoanut    Oil 

1,000,000  gals. 
16,000,000  Ibs. 
74,000,000    '* 

Over  8,000,000  gals. 
337,000,000  Ibs. 
259,000,000    " 

5.  Artificial  Lards. — As  the  high  price  of  butter  and 
the  inadequate  supplies  have  led  to  the  substitution  of 
oleos,  so  has  it  been  in  the  case  of  lard.     The  demand 
is  vastly  greater  than  the  supply  and  today  a  consider- 
able number  of  so-called  "compound  lards"  are  found 
on    the    market.      Such    are    "Suetene,"    "Cottolene," 
"White  Cloud,"  "Snowdrift,"  and  numbers  of  others. 
As  the  names  of  some  indicate,  many  of  them  contain 
more  or  less  of  cotton-seed  oil.     But  as  this  runs  high 
in   olein   it   is   liquid   at    ordinary   temperatures.      The 
public  is  accustomed,  however,  to  a  solid  fat  for  short- 
ening and  for  various   other   food  purposes;   hence,   it 
is   slow   to    accept   a   liquid,   however   equally    good   it 
might  be.     Efforts  were  made,  therefore,  to   overcome 
this  difficulty,  and  these  'have  been  eminently  successful 
as  will  be  shown  later  in  this  chapter. 

6.  Structural  Composition  of  Fats. — With  the  excep- 
tion of  olein  the  fats  mentioned  in  this  chapter  may  be 
regarded  as  derivatives  of  the  paraffins.     Thus,  butane, 
C4H10,  is  the  fourth  in  the  paraffin  series.     The  acid  de- 
rived   from    it,     butyric,     would    have     the     formula, 
C3H7COOH.     Combining  this  acid  with  the  base,  glyce- 
rol,  as  shown  by  the  equation, 

C3H5(HO)3  +  3C3H7COOH  ->  3H20  +  C3H5  (C3H7COO)3 
we  have  butyrin.    As  the  paraffins  are  all  saturated  com- 
pounds, so  are  the  glyceryl  salts  derived  from  them.    To 


ETHEREAL  SALTS,   OILS,   FATS,   SUGARS  217 

illustrate:  Methane,  ethane  and  butane  are  respectively 
represented  by  the  structural  formulas, 

PI  H  H  H  H  H  II 

I  II  I    I     I    I 

H-C-H  H-C-O-H  H-C-C-C-C-H,  and  butyric 

"I  II  I     I      I    I 

H  H  H  HH  HH 

HH  HO 

acid  by  H-C-C-C-C-0-H. 

I    I     I 
HH  H 

In  all  these  it  is  seen  that  every  carbon  atom  is  fully 
saturated;  so  are  the  esters  as  may  be  seen  in  the  fol- 
lowing formula  for  butyrin.  To  the  glyceryl  radical, 
(C3H5)  three  carbon  chains  are  attached,  but  only  one 
is  written  for  the  sake  of  convenience, 

HH  HO 

H-C-C-C-C-0-(C,H,)  =. 
I    I     I 
H  II  H 

7.  The  Olefins. — There  is  another  class  of  hydrocar- 
bons to  which  attention  must  be  directed  in  order  that 
the  preparation  of  compound  lards  may  be  understood. 
These  are  the  olefins,  many  in  number,  of  which  the 
first  few  of  the  series  are  given. 

Ethylene,  C2H4, 

Propylene,  C8H0, 

Butylene,  C4H8, 

Amylene,  C5H10,  also  called  Pentylene, 

Hexylene,  C0H12. 

It  will  be  observed  that  they  are  given  names  derived 
from  those  of  the  paraffins,  with  the  ending  changed. 
There  is  no  olefin  corresponding  to  methane.  These  com- 
pounds may  also  form  acids  and  alcohols  as  in  the  case 


218  APPLIED    CHEMISTRY 

of  the  paraffins.  The  important  distinction  to  be  noticed 
at  this  time  is  that  these  are  unsaturated  compounds. 
A  proof  of  this  was  given  in  the  case  of  ethylene  on  p. 

HH 

I    I 
180.   Structurally,  this  would  be  represented  thus,  -C-C-, 

I     I 
HH 

which  shows  two  of  the  carbon  atoms  with  one  free  bond. 
In  the  same  way  the  acids  and  the  esters  derived  from 
them  would  be  unsaturated.  Therefore,  olein,  belonging 
in  this  group,  is  an  unsaturated  compound.  If  the  for- 
mulas for  stearin  and  olein  be  compared,  it  will  be  ob- 
served that  they  differ  only  by  two  atoms  of  hydrogen, 
yet  one  is  a  hard  white  solid,  and  the  other  a  liquid  at 
ordinary  temperatures.  Without  attempting  to  write  the 
entire  carbon  chain,  they  may  be  compared  thus, 

HHHO 

Chain  of  Carbon-C-C-C-C-0-(C3H5)  =  2  Carbon  Chains, 
I    I     I 
HHH 

H     HO 

Chain  of  Carbon-C-C-C-c'-0-(C3H5)  =2  Carbon  Chains. 
I    I     I 
H     H 

The  first  of  these  is  stearin,  the  second,  olein. 

8.  Hydrogenation  of  Oils. — If  the  above  statements 
are  true  it  would  seem  that  if  it  were  possible  to  cause 
the  unsaturated  carbon  atom  in  olein  to  take  up  two 
additional  atoms  of  hydrogen,  the  olein  should  be 
changed  into  stearin  with  a  corresponding  change  in 
melting  point.  This  has  been  found  possible  and  the 
process  is  called  hydroyenation.  A  current  of  hydrogen 
introduced  into  any  of  these  oils  has  no  effect,  but  if  a 


ETHEREAL  SALTS,   OILS,    FATS,   SUGARS  219 

catalytic  agent  be  used,  more  often  nickel  in  this  case, 
the  unsaturated  olein  takes  up  the  additional  hydrogen 
and  at  room  temperature  becomes  a  white  solid.  The 
process  has  the  greatest  commercial  value.  "Crisco, "  as 
well  as  the  various  compound  lards  mentioned,  are  vegeta- 
ble oils,  thus  hydrogenated,  or  they  are  mixtures  of  the 
same  with  animal  fats.  Wesson  oil  is  cotton-seed  oil  pre- 
pared by  a  certain  process  for  cooking  purposes.  All  the 
edible  vegetable  oils  such  as  those  made  from  corn,  pea- 
nuts, cotton  seed,  soy  beans,  cocoanuts,  arc  now  being 
hydrogenated  and  made  into  pure  white  solid  fats.  They 
are  all  wholesome,  probably  even  more  so  than  those  of 
animal  origin,  because  not  subject  to  disease  and  equally 
valuable  as  energy  and  heat  producers. 

9.  The  Carbohydrates. — The  organic  compounds  con- 
sidered thus  far  in  this  chapter  have  all  been  hydrocar- 
bons and  derivatives  from  them.  There  is  another  very 
important  class  known  as  the  carbohydrates,  which  as 
the  name  indicates  contain  carbon,  hydrogen  and  oxygen. 
The  hydrogen  and  oxygen  with  scarcely  any  exception 
are  in  the  proportion  of  2  to  1.  Three  of  the  most  com- 
mon, which  are  typical  of  the  three  classes  are 

Glucose,  CGH1206,  a  monosaccharide, 
Cane  Sugar,  C^H^O^,  a  disaccharide, 
Starch,   (C6H1005)n,  a  polysaccharide. 

The  prefixes  mono-,  di-  and  poly-  refer  to  the  number  of 
aldehyde  or  ketone  groups  which  the  various  compounds 
in  these  three  classes  contain.  One  aldehyde,  HCOII,  has 
been  studied,  but  the  ketones  are  not  of  sufficient  im- 
portance to  demand  our  attention  here.  The  group  -COII 
is  contained  in  all  aldehydes;  glucose  has  one  of  these 
groups,  cane  sugar  two,  and  starch  several  or  many.  Glu- 
cose is  one  of  several  sugars  with  the  same  empirical  for- 


220  APPLIED    CHEMISTRY 

mula,  found  in  nature  in  various  fruits.  It  is  manufac- 
tured extensively  from  corn  starch.  The  oil  is  first  re- 
moved from  the  corn;  in  water  under  the  action  of  di- 
lute sulphuric  acid,  the  starch  takes  up  two  additional 
atoms  of  hydrogen  and  one  of  oxygen  for  each  saccharide 
group,  thus, 


The  sulphuric  acid  used  is  merely  catalytic  and  is  re- 
moved by  adding  lime  or  some  similar  substance  which 
converts  it  into  an  insoluble  compound,  so  that  it  settles 
out.  The  glucose  is  then  concentrated  and  put  on  the  mar- 
ket mostly  in  the  form  of  a  syrup  under  a  variety  of 
trade  names.  One  of  the  most  advertised  is  "Karo," 
which  may  be  had  in  a  dark  variety,  the  natural  color, 
and  a  light  variety,  which  has  been  bleached  by  sulphur 
dioxide.  Glucose,  while  only  about  three-fifths  as  sweet 
as  cane  sugar,  is  a  wholesome  article  of  food  notwith- 
standing a  popular  prejudice  against  it.  This  has  come 
through  a  misunderstanding  regarding  the  sulphuric  acid 
used  in  the  inversion  of  the  starch.  The  bleached  or  color- 
less syrups  may  sometim.es  contain  a  trace  of  the  gas  used 
in  the  process  of  bleaching,  but  this  objection  cannot  be 
offered  to  the  dark  syrups.  Much  of  the  candy  on  the 
market  contains  more  or  less  glucose.  Probably  the  only 
objection  that  can  be  offered  is  that  it  absorbs  moisture 
from  the  air  more  readily  than  that  made  from  cane 
sugar,  and  thus  in  damp  weather  tends  to  become 
"sticky."  Glucose,  as  a  food,  is  more  readily  assimilated 
than  cane  sugar;  in  fact,  the  latter,  before  assimilation, 
must  be  changed  by  the  digestive  fluids  into  the  monosac- 
charide  variety. 

10.  The  Disaccharides.—  Cane  and  beet  sugar  are  the 
two  most  abundant  of  this  class  and  have  the  same  com- 
position. Their  source  is  well  known  and  need  not  be 


ETHEREAL  SALTS,   OILS,   FATS,  SUGARS  221 

discussed  here.  Milk  sugar,  obtained  as  a  by-product 
from  the  whey  in  cheese  factories,  differs  from  the  two 
already  mentioned  in  that  it  contains  a  molecule  of  com- 
bined water,  thus,  C^H^On.ILO.  Milk  becomes  sour 
through  the  changing  of  this  sugar  into  lactic  acid  just 
as  acetic  acid  is  produced  in  cider  through  the  fermen- 
tation of  the  fruit  sugar  contained  in  the  apple.  The 
lactic  acid  produced  thus  converts  the  casein,  originally 
present  in  the  soluble  form,  into  the  insoluble  variety, 


va 


Fig.  46. — Starch  granules.  The  shape  of  the  granules  is  different  in  the 
various  starch-containing  foods,  so  that  under  the  microscope  the  variety 
may  he  readily  recognized. 

so  that  the  milk  becomes  "curdled."  The  same  thing 
occurs  in  the  stomach  through  the  action  upon  the  casein 
of  the  hydrochloric  acid  always  normally  present. 

11.  Starches. — A  large  number  of  plants  produce 
starch.  The  most  familiar  to  us  are  the  grains,  such 
as  wheat  and  corn,  and  the  potato.  All  have  the  same 
formula,  but  under  the  microscope,  their  granules  are 
very  different  in  shape  (Fig.  46).  The  number  of  sac- 
charide  groups  contained  in  the  molecule  is  not  known 


222  APPLIED  CHEMISTRY 

as  is  indicated  by  the  formula.  Cellulose  is  represented 
by  the  same  empirical  formula,  but  probably  the  value 
of  n  is  different  from  what  it  is  with  the  starches.  It 
would  seem  possible,  judging  from  the  formulas  of 
starch  and  cellulose,  to  convert  such  waste  products  as 
sawdust,  which  is  largely  cellulose,  into  a  monosaccha- 
ride,  as  starch  is  made  into  glucose.  No  method,  how- 
ever, has  ever  been  devised  which  is  cheap  enough,  al- 
though experimentally  it  is  entirely  possible.  When 
dry  starch  is  heated  to  250°  C.  it  is  converted  into  a 
product  called  dextrin;  when  made  into  a  paste,  it  is 
used  instead  of  mucilage  extensively,  especially  upon 
envelopes,  stamps,  and  for  similar  purposes.  It  is  also 
employed  largely  in  sizing  paper,  weighting  cloth,  paper 
for  cardboard,  and  for  sizing  walls  preparatory  to  paper- 
ing. Paper  is  made  from  wood,  straw,  and  various  other 
articles  which  consist  largely  of  cellulose.  Another  organic 
compound  in  the  wood,  known  as  liguin,  is  first  removed 
by  treatment  with  sodium  hydroxide  or  some  other  chemi- 
cal reagent,  and  the  remaining  cellulose  washed  thoroughly 
with  water.  The  pulp  is  then  rolled  into  sheets  and  dried. 
Filter  paper  is  nearly  pure  cellulose. 

Exercises  for  Review 

1.  What   is   an    ester?     How   did  it   receive   the   name?     Name 
three. 

2.  What  is  glycerol?     Formula?     Where  obtained? 

3.  Name  four  esters  of  glycerine. 

4.  Of  what  does  butter  consist?     What  is  mazola? 

5.  What  is   oleomargarine?     What   advantages   do   the   cocoanut 
oleos  have? 

6.  What  is  a  compound  lard?     Name  some  on  the  market. 

7.  Write  the  structural  formula  of  butyric  acid  to  show  it  is  a 
saturated  compound. 

8.  Name  four  olefins.     How  are  they  different  from  the  paraf- 
fins? 


ETHEREAL  SALTS,   OILS,   FATS,   SUGARS  223 

9.  How  docs  olein  differ  from  stearin? 

10.  What  is  meant  by  hydrogenation?     What  effect  does  it  have 
on  an  oil?     Can  stearin  be  hydrogenated  ?     Why? 

11.  What  is  a  carbohydrate?     Name  three  classes  with  example 
of  each. 

12.  What  is  "karo"?     How  made? 

13.  Name  three  disaccharides.     What  is  the  origin  of  lactic  acid 
in  milk? 

14.  How  is  cellulose  different  from  starch? 

15.  How  is  dextrin,  made?     Uses? 

16.  Of  what  does  paper  consist  mainly? 


CHAPTER  XIX 

FOODS  AND  THEIR  BODY  VALUES 

Outline — 

Classes  of  Foods 

Carbohydrates 

(a)   Sugars 

(7?)    Starches 

(c)   Cellulose 
Oils  and  Fats 
Proteins 
Minerals 

1.  Kinds  of  Foods. — The  various  foods  used  may  be 
classified  as  carbohydrates,  oils  and  fats,  and  proteins, 
to  which  some  add  inorganic  or  mineral  foods   which 
may  be  made  to  include  water. 

2.  Carbohydrates. — The  carbohydrates  most  commonly 
used  as  foods  are  the  various  sugars,  starch  and  cellu- 
lose.    When  sucrose,  a  general  term  for  either  cane  or 
beet  sugar,   is  boiled  in   the   presence   of   an   acid,   it   is 
slowly  changed  into  glucose  and  fructose,  both  mono- 
saccharides,  called  in  this  case,  invert  sugars.    The  proc- 
ess is  called  inversion.     As  the  invert  sugar  obtained  is 
not  as  sweet  as  the  cane  sugar  used,  in  stewing  any  acid 
fruit  for  table  use  it  is  better  not  to  add  the  sugar  till 
the  fruit  is  about  done.    By  this  plan  less  inversion  takes 
place  and  less  sugar  is  required  to  render  the  fruit  pal- 
atable.    Not  only  do  acids  have  the  catalytic  action  of 
inverting  sugar,  but  certain  enzymes  as  well.     In  our 
foods  before  sucrose  is  assimilated  by  the  body  it  is  con- 
verted into  invert  sugar  by  the  enzymes  of  the  diges- 
tive fluids..    The  sugars  and  starches  serve  mainly  as 

224 


FOODS    AND    THEIR   BODY    VALUES  225 

fuel  and  energy  producers.  Since  they  contain  suffi- 
cient oxygen  to  convert  the  hydrogen  present  into  wa- 
ter, it  is  the  carbon  content  alone  that  determines  the 
relative  fuel  value  of  a  carbohydrate.  In  the  body  it 
combines  with  oxygen  obtained  through  the  lungs  and 
heat  results,  just  as  if  so  much  carbon  in  the  form  of 
coal  were  burned  in  a  stove. 

Starchy  foods  are  obtained  mainly  from  the  various 
grains,  wheat,  corn,  rice,  rye,  oats  and  barley;  also  from 
the  potato,  tapioca,  arroAvroot  and  sago.  Bananas  con- 
tain about  22  per  cent  of  carbohydrates,  much  of  which 
before  the  fruit  is  fully  ripe  is  in  the  form  of  starch. 
When  starchy  foods  are  toasted,  a  portion  of  the  starch 
is  converted  into  dextrin,  as  is  the  outer  portion  of  the 
crust  of  bread  in  baking.  It  is  sweeter  than  starch, 
more  soluble  and  more  easily  digested.  All  starchy 
foods,  before  digestion  can  take  place,  must  be  hydro- 
lyzed  or  converted  into  invert  sugar:  this  is  partly  ac- 
complished in  mastication  through  the  action  of  the 
enzymes  in  the  saliva.  The  equation  shows  the  change, 
which  is  altogether  catalytic, 


Used  in  the  body  carbohydrates  serve  two  purposes, 
giving  energy  for  muscular  exertion  and  warming  of 
the  body.  When  assimilated  into  the  circulatory  sys- 
tem they  meet  the  oxygen  and  chemical  union  takes 
place,  accompanied  by  heat.  Any  excess  may  be  stored 
up  in  the  muscles  and  liver  in  the  form  of  an  animal 
starch  called  glycogen.  This  may  be  used  whenever  an 
insufficient  amount  is  furnished  by  the  daily  food. 

Cellulose  is  found  in  many  of  our  foods  and  is  a  car- 
bohydrate as  seen  in  the  preceding  chapter,  but  it  is 
not  an  energy  producer,  for  the  reason  that  it  is  not 


226  APPLIED    CHEMISTRY 

digestible.  It  is  the  enclosing  wall  of  starch  granules; 
it  is  abundant  in  the  stems  of  plants.  As  maturity  is 
reached  in  many  vegetable  foods,  the  quantity  of  cellu- 
lose increases.  This  is  seen  in  asparagus,  string  beans, 
turnips,  beets,  celery  and  various  others.  It  is  what  is 
spoken  of  as  crude  fiber  in  grains;  the  outside  cover- 
ing of  wheat,  corn,  unpolished  rice  and  other  cereals. 
It  is  not  capable  of  inversion  by  any  of  the  enzymes  of 
the  body  and  for  that  reason,  as  stated  above,  is  indi- 
gestible. Nevertheless,  it  plays  a  far  more  important 
part  in  digestion  and  the  bodily  health  than  most  of  us 
realize.  It  serves  as  a  stimulant  to  the  secretion  of 
the  fluids  necessary  for  digestion  and  excretion  and 
aids  in  increasing  peristaltic  action;  in  other  words,  it 
is  a  body-regulator  food.  Domestic  animals  such  as 
the  horse  and  cow  use  large  amounts  of  what  is  called 
" roughness"  or  hay,  much  of  which  is  cellulose.  Fed 
on  concentrated  foods  entirely  they  lose  appetite  and 
quickly  become  a  prey  for  all  sorts  of  diseases.  In  all 
probability  a  large  proportion  of  the  bodily  ills  of  man- 
kind may  be  traced  directly  to  the  use  of  foods  too 
much  refined  and  lacking  in  crude  fiber  or  cellulose. 
Herein  lies  the  health  value  of  graham  and  bran  breads 
and  whole  wheat  foods  and  others  of  similar  character. 
Pectin  is  another  vegetable  carbohydrate  found  in  the 
juices  of  many  fruits  and  in  the  inner  portion  of  the 
peeling  of  the  orange  and  other  citrus  fruits.  It  is 
the  principle  involved  in  the  making  of  jellies.  It  is 
coagulated  by  acids  and  also  by  sugar.  In  boiling  fruit 
juice  the  water  is  removed  and  the  pectin  concentrated. 
The  point  is  finally  reached  where  coagulation  takes 
place  upon  cooling.  This  is  determined  by  the  house- 
wife by  frequently  testing  small  portions  in  a  dish. 
For  years  numerous  attempts  were  made  to  prepare 


FOODS    AND    THEIR   BODY   VALUES  227 

jellies  from  the  cheaper  grades  of  oranges  regarded  as 
unsalable  by  the  packing  houses,  but  all  without  suc- 
cess. Finally,  it  was  found  that  in  the  orange  the  pectin 
is  contained  in  the  white  portion  of  the  peeling  and 
not  in  the  juice.  Therefore  when  this  portion  is  used 
with  the  juice  of  the  fruit  the  operation  is  successful ; 
and  orange  jelly  and  marmalade  are  now  common  arti- 
cles of  commerce. 

3.  Oils  and  Fats. — These  foods  are  also  heat  and  en- 
ergy producing.     One  pound  of  this  class  is  about  the 
equivalent   of   2%   pounds   of   carbohydrates.      This   is 
because  the  amount  of  oxygen  contained  is  much  less  in 
proportion  in  the  fats  and  oils.    They  produce  heat  and 
energy  in  the  same  manner  as  the  carbohydrates.     In 
good  assimilation  any  excess  of  such  foods  is  stored  up 
as  glycogen  in  the  liver,  or  as  adipose  tissue  in  various 
parts  of  the  body,  presumably  to  be  used  in  cases  of 
forced  abstinence  or  as  other  needs  might  come. 

4.  Protein    Foods. — Proteins     are    primarily    muscle 
builders  and  not  energy  producing.    It  is  true  they  may 
serve  as  body  fuel,  but  as  nitrogen  is  not  oxidizable, 
they  are  poor  in  this  respect  and  should  never  be  used 
with  this  idea  in  view.    The  body  contains  about  18  per 
cent  of  proteins.     Whenever  work  is  done,  or  muscular 
exercise  of  any  kind-  is  taken,  some  of  the  cells  of  the 
tissues  are  torn  down  and  must  be  replaced.    Plants  have 
the  power  of  building  their  own  protein  from  the  carbon 
dioxide  inhaled  from  the  air  together  with  the  nitrogen 
and  water  absorbed  from  the  soil.     Some  few,  the  leg- 
umes, through  the  aid  of  bacteria,  may  even  obtain  the 
needed  nitrogen  from  the  air.     But  no  animal  has  such 
powrer.    It  must  use,  for  replacing  wasted  muscular  tis- 
sue, protein  already  formed ;  this  may  be  either  of  ani- 
mal or  vegetable  origin.    Such  foods  as  eggs,  lean  meat, 


228 


APPLIED    CHEMISTRY 


milk,  cheese,  beans,  peas  and  other  legumes  are  rich  in 
protein.  Several  grains  also  furnish  considerable  pro- 
tein if  the  whole  of  the  grain  is  used.  As  protein  serves 
mainly  to  restore  wasted  muscular  tissue,  the  amount 
needed  depends  upon  the  amount  of  bodily  exercise 
taken.  In  general,  it  may  be  said  that  not  over  3  ounces, 
80  grams,  per  day,  are  necessary,  often  much  less. 
Those  with  sedentary  employment  require  but  little, 
while  those  engaged  in  manual  labor  need  much.  Too 
little  regard  is  paid  to  this  fact,  with  serious  results 
to  the  bodily  health.  When  carbohydrates  are  oxidized 
in  the  body,  carbon  dioxide  and  water  are  the  sole  prod- 
ucts and  these  are  eliminated  largely  through  the  lungs. 
Proteins,  being  nitrogenous  foods,  are  converted  into 
urea,  (NH2)2CO,  and  this  is  eliminated  through  the 
perspiratory  glands  and  by  the  kidneys.  In  case  of  ex- 

TABLE  OF  FOOD  VALUES  OF    CERTAIN  NUTS 
From   Farmer's   Bulletin,   No.   332- 


NUT 

WASTE 

% 

WATER 

PRO- 
TEIN 

PAT 

CARBO- 
HYDRATE 

FUEL    VALUE 
PER     POUND 
CALORIES 

Pecans 

50 

3.4 

12.1 

70.7 

12.2 

3325 

Hickory 
Walnut 

62 
59 

3.7 
3.4 

15.4 

18.2 

67.4 
60.7 

11.4 

16.0 

3240 
3100 

Cocoanuts 

35 

13.0 

6.6 

56.2 

22.6 

2825 

Peanuts 

27 

7.4 

29.8 

43.5 

17.1 

2625 

Chocolate 



5.9 

12.9 

48.7 

30.3 

2770 

Cocoa 

— 

4.6 

21.6 

28.9 

37.7 

2255 

SOME   DRIED   FRUITS 


FRUIT 

WASTE 

% 

WATER 

PRO- 
TEIN 

FAT 

CARBO- 
HYDRATE 

CALORIES 

Dates 
Raisins 
Figs 
Prunes 
Apples 

10 
10 

15 

15.4 

14.6 
18.8 
22.3 

28.1 

2.1 

2.6 

4.3 
2.1 
1.6 

2.8 
3.3 
0.3 

2.2 

78.4 
76.1 
74.2 
73.3 
66.1 

1575 
1560 
1435 
1370 
1320 

FOODS    AND    THEIR    BODY    VALUES 


229 


SOME    FRESH    FRUIT 


FRUIT 

WASTE 

% 

WATER 

PRO- 
TEIN 

FAT 

CARBO- 
HYDRATE 

CALORIES 

Banana 

35 

75.3 

1.3 

0.6 

22.0 

450 

•Grapes 

25 

77.4 

1.3 

1.6 

19.2 

435 

Plums 

5 

78.4 

1.0 

20.1 

380 

Cherries 

5 

80.9 

1.0 

0.8 

16.7 

355 

Pears 

10 

84.4 

0.6 

0.5   '          14.1 

285 

Apples 

25 

84.6 

0.4 

0.5 

14.2 

285 

Orange 

27 

86.9 

0.8 

0.2             11.6 

235 

Peach 

18 

89.4 

0.7 

0.1               9.4 

185 

FOOD  VALUES  OF  CEREAL  PRODUCTS 


NAME 

WATER 

% 

PRO- 
TEIN 

FAT 

CARBO- 
HYDRATE 

CALORIES 

Crackers 

5.9 

9.8 

9.1 

73.1 

1875 

Rolled  Oats 

7.7 

16.7 

7.3 

66.2 

1800 

Shredded   Wheat 

8.1 

10.5 

1.4 

77.9 

1660 

Graham  Flour 

11.3 

13.3 

2.2 

71.4 

1630 

Macaroni 

10.3 

13.4 

0.9 

74.1 

1625 

Hominy 

11.8 

8.3 

0.6 

79.0 

1610 

White  Flour 

12.8 

10.8 

1.1 

74.8 

1610 

Rice 

12.3 

8.0 

0.3 

79.0 

1590 

White  Bread 

35.0 

9.1 

1.6 

53.3 

1200 

Graham  Flour 

35.7 

8.9 

1.8 

52.1 

1180 

FOOD  CONTENT  OF  CERTAIN  VEGETABLES 


NAME 

WATER 

% 

PRO- 
TEIN 

FAT 

CARBO- 
HYDRATE 

CALORIES 

Sweet    Potato 

20 

1.8 

0.7 

27.4 

560 

Irish      Potato 

20 

2.2 

0.1 

18.4 

380 

Parsnips 

20 

1.6 

0.5 

13.5 

295 

Onions 

10 

1.6 

0.3 

9.9 

220 

Beets 

20 

1.6 

0.1 

9.7 

210 

Carrots 

20 

1.1 

0.4 

9.3 

205 

Turnips 

30 

1.3 

0.2 

8.1 

180 

Cabbage 

15 

1.6 

0.3 

5.6 

145 

Cauliflower 

— 

1.8 

0.5 

4.7 

140 

Spinach 

— 

2.1 

0.3 

3.2 

110 

Celery 

20 

1.1 

0.1 

3.3 

85 

Cucumber 

15 

0.8 

0.2 

3.1 

80 

Green  Peas 

45 

7.0 

0.5 

16.9 

455 

String  Beans 

n 

2.3 

0.3 

7.4 

190 

Squash 

50 

1.4 

0.5 

9.0 

210 

Tomatoes 

10 

0.9 

0.4 

3.9 

105 

230  APPLIED    CHEMISTRY 

cess,  uric  acid  forms  and  tends  to  accumulate  in  the 
muscles  and  about  the  joints  and  causes  rheumatism. 
Those  in  sedentary  employments,  therefore,  should  use 
little  meat  or  other  nitrogenous  foods.  Nitrogenous 
foods  in  decomposing  often  produce  what  are  called 
amines.  These  are  substitution  products  of  ammonia, 
one  of  which  is  NH2CH3,  methyl  amine.  Some  of  these 
are  very  poisonous  and  are  called  ptomains.  In  tables 
showing  content  of  protein  in  various  food  products, 
the  amount  is  often  given  in  terms  of  nitrogen.  As  on 
an  average  the  nitrogen  in  a  protein  is  16  per  cent,  to 
determine  the  amount  of  protein  contained  the  nitro- 
gen must  be  multiplied  by  6.25.  The  preceding  tables 
show  the  food  content  and  the  fuel  or  calorific  value 
of  a  large  number  of  common  articles  of  diet : 

5.  Mineral  Foods. — In  all  foods  used  there  are  small 
quantities  of  mineral  matter  or  ash.  These  come  from 
the  soils  and  are  taken  up  by  the  growing  plant.  While 
the  amounts  are  small,  certain  portions  seem  necessary 
for  health.  The  blood  owes  its  color  to  the  presence  of 
iron  compounds,  and  certain  foods  especially  are  rela- 
tively rich  in  these.  Such  are  eggs,  milk,  peas,  beans, 
figs,  dates,  raisins,  wheat,  rye,  barley,  and  spinach.  Cal- 
cium and  phosphorus,  usually  combined  as  a  phosphate, 
are  especially  needed  in  youth,  but  more  or  less  at  all 
times.  The  dry  bone  is  over  50  per  cent  calcium  phos- 
phate, while  other  portions  of  the  body  also  contain 
smaller  amounts.  This  must,  therefore,  be  supplied. 
Such  foods  as  milk,  eggs,  cheese,  whole  wheat,  nuts 
and  beans  are  rich  in  phosphorus.  White  flours  are 
made  by  milling  off  the  outer  portions  of  the  grain; 
hence,  the  cellulose  and  the  mineral  portions  are  lost 
as  foods  with  serious  consequences  to  the  bodily  health. 
In  the  body  are  also  found  sodium,  potassium,  magne- 


FOODS    AND    THEIR    BODY    VALUES 


231 


slum,  chlorine  and  sulphur.  More  than  sufficient  so- 
dium and  chlorine  are  supplied  in  the  common  salt 
used.  Sulphur  is  contained  in  such  foods  as  eggs,  and 
often  in  other  protein  foods.  Magnesium  and  potassium 
are  found  in  various  nuts,  cocoa,  beans,  peas,  prunes, 


Fig.  47. — Foods  rich  in  iron.  (From  Greer's  Textbook  of  Cooking.) 
a,  Peas;  b,  figs;  c,  wheat;  d,  lentils;  c,  spinach;  /,  dates;  g,  eggs;  h,  rye;  i, 
beef;  j,  beans;  k,  raisins;  I,  lima  beans. 

figs,  raisins,  oats  and  rye.  The  following  tables  give 
the  quantity  of  mineral  matter  contained  in  a  number 
of  common  articles  of  diet.  The  value  of  water  in  the 
human  economy  has  been  discussed  elsewhere. 

FOODS  RICH  IN  IKON 

The  following  contain  .003  per  cent  or  more 
Beans,  dry  Lean  beef  Whole  barley 

Dates  Peas,  dry  Whole  rye 

Fggs  Eaisins  Whole  wheat 

Figs,  dried  Spinach 

FOODS  RICH  IN  PHOSPHORUS 
The  following  contain  .9  per  cent  or  more 
B'eans,  dry  Cocoa  Peas,  dry 

Cheese  Eggs,  the  yolk  Whole  wheat 

Chocolate  Peanuts 


232 


APPLIED    CHEMISTRY 


Fig.  48. — Foods  rich  in  phosphorus.  (From  Greer's  Textbook  of  Cook- 
ing.) a,  Peas;  b,  chocolate;  c,  beans;  d,  peanuts;  e,  whole  wheat;  /,  cheese; 
g,  cocoa;  h,  yolk  of  egg. 

Figs.  47  and  48  show  graphically  what  is  given  in  the 
tables.     (From  Greer's  Textbook  of  Cooking.) 

Exercises  for  Review 

1.  Name  the  four  classes  of  foods. 

2.  What  is  meant  by  inversion?    Why  should  the  sugar  be  added 
after  the  fruit  has  about  finished  cooking? 

3.  Why  is  cellulose  not  digestible?     Of  what  value  is  it  to  the 
body?     What  is  meant  by  crude  fiber? 

4.  What  is  pectin?     Of  what  practical  value  is  it  in  the  house- 
hold?    Where  is  it  found  in  most  fruits?     Any  exception? 

5.  What  is  the  use  of  carbohydrate  foods  in  the  body?     Why  is 
a  fat  of  greater  fuel  value  than  a  sugar? 

6.  Explain  how  the  heat  is  produced  in  the  body.     How  are  the 
products  of  combustion  in  the  body  eliminated? 

7.  Of  what  do  protein  foods  consist?     Name  some  typical  ones. 

8.  What  value  has  a  protein  food  to  the  body?     How  much  of 
this  kind  of  food  is  needed  per  day? 

9.  Into  what  is  protein  food  converted  when  it  has  been  used  in 
the  body?     How  is  it  removed? 

10.  In  case   of  excess  of  protein   foods  what  is  apt  to   follow? 
How  remove  this  condition? 

11.  Name  the  more  common  mineral  foods.     From  what  may  the 
three  most  important  be  obtained? 

12.  What   do   most   "tonics"    contain?     What   is   the   supposed 
purpose? 


CHAPTER  XX 

SOLUTION  AND  IONIZATION 

Outline- 
Meaning  and  Kinds  of  Solution 
Concentration  of  Solutions 
Characteristics  of  Solutions 

(a)   Change  in  Freezing  Point 

(&)   Eise  in  Boiling  Point 

(c)   Difference  in  Density 
Law  of  Variation 
Noted  Exceptions 
Cause  of  Variation 
Conductivity  of  Solutions 
Dissociation 

(a)   By  Heat 

(&)   By  Solution 
lonization  and  Ions 
Ions  and  Valence 
Ions  and  Chemical  Action 

1.  Definition  of  Solution. — As  generally  defined  a  so- 
lution is  a  homogeneous  mixture  of  two  or  more  sub- 
stances. Usually  we  think  of  it  as  a  solid  in  a  liquid, 
for  such  are  the  more  common.  The  solvent  is  the  sub- 
stance of  greater  amount,  while  the  solute  is  the  other. 
Thus,  if  a  few  grams  of  salt  be  dissolved  in  a  liter  of 
water,  the  salt  is  the  solute  and  the  water  is  the  solvent. 
There  are  several  kinds  of  solutions  besides  that  of  a 
solid  in  a  liquid.  For  example,  air  is  a  solution,  in 
which  the  nitrogen  is  the  solvent.  Soda  water  is  a 
solution  of  a  gas,  carbon  dioxide,  in  water;  a  silver 
dollar  is  a  solution  of  10  parts  of  copper  in  90  of  silver. 
However,  as  solutions  of  solids  in  liquids  are  by  far  the 
most  common,  it  is  with  them  that  this  chapter  deals. 

233 


234  APPLIED    CHEMISTRY 

2.  Solution   Concentration. — The   properties    of    solu- 
tions differ  from  those  of  the  solvent.     For  the  sake  of 
comparisons  it  is  necessary  to  agree  upon  some  stand- 
ard when  speaking  of  the  strength  of  a  solution.     If  a 
gram  molecular  weight  of  any  substance  be  dissolved 
in  a  liquid  so  as  to  make  one  liter  of  the  mixture,  the 
solution  is  said  to  have  a  concentration  of  one,  and  is 
marked  C±.     If  a  liter  of  a  solution  contains  2  gram 
molecular  weights  of  the  solute,  its  concentration  is  two, 
marked  C2.    Obviously,  a  gram  molecular  weight  of  sugar 
would  contain  the  same  number  of  molecules  as  a  gram 
molecular  weight  of  salt,  although  the  former  would  con- 
tain 342  grams  and  the  latter  only  58.46  grams.    So  in  all 
solutions  with  a  concentration  of  one  there  would  be  the 
same  number  of  molecules  of  the  solute. 

3.  Characteristics  of  Solutions. — As  there  is  always 
a  diminution  of  volume  when  two  substances  are  mixed 
homogeneously,   the  specific   gravity  of  the   solution  is 
always   greater   than   that    of   the   solvent.      Again,    the 
freezing  point  is  always  lower  than  that  of  the  solvent, 
and  the  boiling  point  is  higher,  or,  as  it  is  usually  ex- 
pressed, the  vapor  pressure  is  lowered.    A  little  thought 
will   make   all   three   statements   apparent.     As   a   small 
handful  of  salt  may  be  dissolved  in  a  quart  of  water  with- 
out greatly  increasing  the  volume,   evidently  the  water 
per  cubic  centimeter  is  heavier  than  before  the  salt  was 
added.      Heat   is   merely   a   form   of   molecular   energy; 
when  a  body  is  warmed  its  molecules  are  made  to  move 
faster;  when  cooled  their  motion  becomes  slower.    There- 
fore, since  there  are  more  molecules  in  a  given  volume  of  a 
solution  than  in  the  same  volume  of  the  solvent,  it  would 
take  more  heat  energy  to  set  them  in  motion  or,  on  the 
other  hand,  to  stop  them  than  if  dealing  with  the  pure 
solvent.     In  other  words,  speaking  of  cold  as  if  it  were 


SOLUTION    AND   IONIZATION  235 

a  force,  it  would  require  a  greater  degree  of  cold  to 
"slow  down"  the  larger  number  of  molecules  in  the  solu- 
tion than  it  would  the  fewer  number  in  the  solvent,  that  is 
it  is  harder  to  freeze  salt  water  than  pure.  Likewise,  in 
bringing  a  solution  to  the  boiling  point,  there  would  be 
more  molecules  to  which  there  must  be  imparted  a  certain 
velocity  before  boiling  begins,  so  the  temperature  would 
be  higher  before  the  boiling  is  reached.  From  the  fact 
that  a  liquid  begins  to  boil  when  the  pressure  of  the 
vapor  passing  off  from  it  equals  or  is  slightly  in  excess  of 
the  atmospheric  pressure  above  it,  we  usually  say  the 
vapor  pressure  is  lowered  instead  of  saying  the  boiling 
point  is  raised,  but  both  expressions  mean  the  same  thing. 
4.  Concentration  and  Freezing  Point  Lowering.— 
Since  all  solutions  with  a  concentration  of  one  contain 
the  same  number  of  molecules  of  the  solute  per  liter, 
it  would  seem  from  the  kinetic  viewpoint  that  the  freez- 
ing point  of  all  solutions,  no  matter  what  the  solute, 
would  be  lowered  the  same  for  the  same  solvent.  That 
is,  if  pure  water  freezes  at  0°  C.  and  a  solution-  contain- 
ing a  gram  molecule  of  sugar  per  liter  freezes  at  -1.8° 
C.,  we  should  expect  a  solution  of  alcohol  containing 
a  gram  molecule  per  liter  also  to  freeze  at  1.8°  below 
zero.  Likewise  we  should  expect  such  solutions  with 
a  concentration  of  two,  that  is  with  2  gram  molecules 
of  the  solute  per  liter,  to  freeze  at  -3.6°.  If  such  experi- 
ments are  made,  using  any  of  the  soluble  organic  com- 
pounds mentioned  in  the  preceding  chapters,  our  ex- 
pectations are  realized.  These  facts,  then,  are  stated 
in  this  conclusion,  that  the  lowering  of  the  freezing 
point  of  a  solution  is  directly  proportional  to  the  con- 
centration. Briefly  it  is  expressed  thus, 

L  oc  C, 
in  which  L  means  lowering  of  freezing  point  and  C  the 


236 


APPLIED    CHEMISTRY 


concentration,  and  the  sign,  oc  ?  varies  as.  Experiments 
made  upon  the  lowering  of  the  vapor  pressure  of  such 
solutions,  show  like  results,  so  that  the  same  formula 
may  be  applied  to  both  cases.  In  tabular  form  below 
are  shown  some  of  the  solutions  comnionly  used  with 
results  upon  the  freezing  point : 

TABLE  OF  FREEZING  POINT    LOWERING 


SUBSTANCE 

CONCENTRA- 
TION 

FREEZING 
POINT 

GRAMS 
PER     LITER 

Alcohol 

C  =  l 

-1.8 

46 

Glucose 

C  =  l 

-1.8 

186 

Cane  Sugar 

0  =  1 

-1.8 

342 

Glycerine 

0  =  1 

-1.8 

92 

Alcohol 

C  =  2 

-3.6 

92 

Glucose 

C  —  2 

-3.6 

360 

Cane  Sugar 

C  =  2 

-3.6 

684 

Glycerine 

C  =  2 

-3.6 

184 

Alcohol 

C  =  3 

-5.4 

138 

The  results  given  above  have  disregarded  slight  varia- 
tions due  to  experimental  errors  or  otherwise  easily 
accounted  for;  they  show  conclusively  Avhat  was  pre- 
viously stated  that  the  lowering  of  the  freezing  point  de- 
pends upon  the  concentration. 

5.  Exceptions  to  the  Above. — It  will  be  noticed  that 
all  the  substances  given  in  the  table  are  organic  com- 
pounds. We  should  expect  the  same  results,  however, 
with  the  inorganic  compounds,  such  as  common  salt, 
sulphuric  acid,  potassium  chloride,  and  others  familiar 
to  us.  When  such  are  tried,  using  a  concentration  of 
one,  the  same  as  before,  so  as  to  introduce  the  same 
number  of  molecules  per  liter,  the  results  do  not  agree 
at  all.  In  some  cases  the  freezing  point  is  lowered 
nearly  twice  as  much,  in  others  nearly  three  times,  and 
still  others  nearly  four  times  as  much  as  expected. 


SOLUTION    AND   IONIZATION  237 

6.  Cause  of  This  Irregularity. — It  lias 'been  observed 
that  chemical  reactions  between  substances  perfectly 
dry  are  practically  nil.  Pure  dry  hydrogen  chloride  does 
not  react  with  zinc.  It  has  been  said  elsewhere,  Chapter 
I,  that  compounds,  inorganic,  are  composed  of  an  elec- 
tropositive and  an  electronegative  portion  and  that  each 
gives  a  separate  test.  In  the  absence  of  all  water  such 
tests  cannot  be  made.  With  the  organic  compounds  this 
is  not  true.  They  are  not  composed  of  a  positive  and  a 
negative  part  and  tests  with  them  are  tests  upon  the  sub- 
stance as  a  whole.  It  seems  then  that  when  an  inorganic 
compound  is  dissolved  in  water,  in  some  way  the  posi- 
tive and  negative  portions  are  separated  from  each 
other  so  that  each  may  be  tested.  Further,  it  was  no- 
ticed that  such  compounds  as  common  salt,  potassium 
chloride,  hydrochloric  acid,  Ammonium  chloride  and 
many  others,  which  were  possible  of  separation  into 
only  twro  particles,  one  positive  and  one  negative,  always 
gave  a  lowering  of  freezing  point  almost  double  that 
of  the  organic  compounds  when  concentration  of  one  was 
used.  Further,  such  compounds  as  calcium  chloride, 
CaCl2,  barium  chloride,  BaCl2,  sulphuric  acid,  H2S04, 
calcium  hydroxide,  Ca(HO)2  and  many  others  capable  of 
breaking  up  into  three  portions,  two  positive  and  one 
negative  or  one  positive  and  two  negative,  in  concen- 
trations of  one  gave  a  lowering  of  freezing  point  nearly 
three  times  what  the  organic  compounds  did  with  the 
same  concentration.  Again,  aluminum  chloride,  A1C13, 
phosphoric  acid,  H3P04,  capable  of  breaking  up  into 
four  parts,  gave  a  lowering  of  the  freezing  point  almost 
four  times  that  given  by  the  organic  compounds  in  so- 
lutions of  the  same  strength.  From  conclusions  already 
reached  in  the  case  of  the  organic  compounds, — namely, 
that  the  lowering  is  proportional  to  the  concentration, 


238  APPLIED    CHEMISTRY 

it  came  to  be  believed  from  the  above  observations  that 
in  water  the  inorganic  compounds  are  broken  up  into 
parts  and  exist  there  not  as  molecules  but  as  parts  of 
molecules.  If  this  be  true,  a  solution  of  potassium  chlo- 
ride, for  example,  would  have  as  many  particles  to  be 
"slowed  down"  in  their  movement  as  if  the  concentration 
were  two;  that  is,  the  freezing  point  should  be  lowered 
3.6°.  Likewise,  such  substances  as  sulphuric  acid,  or  cal- 
cium chloride  in  solution  would  contain  as  many  parti- 
cles as  of  the  organic  compounds  with  a  concentration  of 
three,  and  should  give  a  lowering  of  5.4°. 

7.  Variation  from  Regular  Lowering. — In  all  these 
cases,  however,  the  lowering  falls  short  of  the  theoretic 
amount,  as  shown  by  the  following  table: 

LOWERING  OF  FREEZING  POINTS 


Substance 

Concentration 

Degrees  Lowered 

Cane  Sugar 

1 

1.8 

Grain  Alcohol 

1 

1.8 

Sodium  Chloride 

1 

3.5 

Calcium  Chloride 

1 

5.1 

Aluminum  Chloride 

1 

6.8 

Thus  it  will  be  seen  that  the  greater  the  number  of  pos- 
sible particles  into  which  the  compound  may  be  broken 
the  greater  the  variation  from  the  theoretic  value.  Ac- 
cording to  the  kinetic  theory,  not  only  are  the  mole- 
cules of  a  body  in  motion,  but  the  atoms  likewise  in  the 
molecule.  Some  years  ago  it  was  shown  by  the  great 
Dutch  chemist,  van't  Hoff  that  in  dilute  solutions  the 
molecules  of  the  solute  are  at  such  distances  from  each 
other  that  they  obey  all  the  gas  laws.  In  these  cases, 
therefore,  the  parts  into  which  the  molecules  are  broken 
would  be  moving  in  all  directions,  and  in  all  probability 


SOLUTION    AND   IONIZATION  239 

would  collide  more  or  less  frequently.  For  example,  if 
potassium  chloride  is  broken  up  into  potassium  and 
chlorine  particles,  in  their  movement  the  potassium  and 
chlorine  would  more  or  less  frequently  collide  and  thus 
a  molecule  of  the  salt  would  be  reformed.  Among  bil- 
lions of  particles  with  a  rapid  motion  these  collisions 
would  be  frequent,  so  that  there  Avould  always  be,  ex- 
cept in  cases  of  very  great  dilution,  a  very  apprecia- 
ble number  of  the  molecules  not  broken  up.  Therefore, 
the  number  of  particles  in  the  solution,  to  be  "slowed 
down,"  would  never  be  quite  double  the  number  of  the 
molecules,  and,  hence,  the  freezing  point  would  not  be 
lowered  fully  twice  as  much  as  in  the  case  of  the  organic 
compounds.  The  same  way  with  the  calcium  chloride,  alu- 
minum chloride  and  others :  there  being  more  particles  per 
degree  of  concentration,  since  each  molecule  may  break  up 
into  three  or  four  parts,  collisions  would  be  more  frequent, 
more  molecules  would  exist  intact,  and  the  lowering 
would  vary  further  from  three  or  four  times  the  theo- 
retic amount. 

8.  Conductivity. — It  was  long  ago  observed  that  such 
substances  as  sugar,  and  the  organic  bodies  are  not  con- 
ductors of  electricity,  either  by  themselves  or  dissolved 
in  water.  It  has  also  been  seen  that  pure  water  is  not  a 
conductor.  Inorganic  compounds,  which  have  been 
found  to  give  very  irregular  results  in  lowering  of  freez- 
ing point,  are  not  conductors  when  in  the  solid  form,  but 
dissolved  in  water  are  almost  universally  good  conduc- 
tors. Such  substances  are  spoken  of  as  electrolytes, 
while  those  which  will  not  conduct  a  current  when  dis- 
solved in  water  are  called  nonclectrolytes.  From  the  above 
observations  and  further,  that  when  solutions  of  the  inor- 
ganic compounds  are  electrolyzed  the  metal  always  ap- 
pears at  the  cathode  and  the  nonmetal  at  the  anode,  it 


240  APPLIED    CHEMISTRY 

was  thought  possible  that  the  positive  particles  might  be 
the  means  of  conducting  the  current  through  the  solution 
and  of  giving  it  up  to  the  negative  electrode.  Further- 
more it  was  concluded  that  organic  compounds  are  not 
conductors,  because  in  water  they  are  not  broken  up  into 
particles  so  as  to  make  it  possible  for  one  portion  to  be 
attracted  toward  the  negative  electrode. 

9.  Dissociation. — It  has  been  seen  in  a  very  consid- 
erable number  of  cases  that  at  different  temperatures 
substances  may  exist  with  molecules  of  differing  com- 
position. Thus,  nitrogen  peroxide,  at  a  temperature  of 
about  23°  C.,  has  a  molecular  weight  of  92,  while  at 
about  135°  it  is  only  46,  and  at  temperatures  between 
these  two  it  varies,  being  lower  as  the  temperature  is 
raised.  As  the  molecular  weight  of  92  would  correspond 
to  the  formula,  N204,  and  46  to  that  of  N02,  there  can 
be  only  one  explanation  and  that  is  that  heat  decom- 
poses nitrogen  tetroxide,  and  at  a  certain  point  this 
decomposition  is  complete,  whereas  at  temperatures  lower 
than  this  there  are  always  present  molecules  of  the 
greater  density  mixed  with  the  lighter  ones.  This  is 
shown  by  the  equation, 

N204  *±  2N02, 

which  means  that  the  process  is  reversible  and,  what  is 
more,  is  probably  occurring  at  all  times.  When  the 
temperature  is  lowered  the  reverse  action  is  more  rapid 
than  the  direct  till  a  certain  definite  proportion  is  reached 
when  equilibrium  obtains.  Such  a  reaction  as  this  is 
called  dissociation.  Defined,  dissociation  is  the  decomposi- 
tion of  a  substance  and  the  reforming  of  the  same  by  the 
union  of  the  products,  when  the  decomposing  cause  is  re- 
moved. Likewise,  ammonium  chloride,  heated,  decom- 
poses into  ammonia  and  hydrogen  chloride,  but  when  the 


SOLUTION    AND    IONIZATION  241 

two  gases  are  carried  away  from  the  source  of  heat  they 
recombine  to  form  ammonium  chloride.  Thus, 

NH4C1  *±  NII3  +  HC1. 

Again,  iodine  vapor,  below  700°  C.  shows  a  density  of 
about  127  compared  to  hydrogen  or  a  molecular  weight 
of  254,  which  indicates  I2  for  the  formula.  Above  700° 
C.  the  density  rapidly  decreases  and  at  about  1,700  it  is 
only  half  what  it  was  at  700.  The  same  thing  has  occurred 
as  in  the  case  of  the  nitrogen  peroxide  and  may  be  repre- 
sented thus, 

I2  ?=>  21. 

Many  others  might  be  given.  Such  cases  are  spoken  of 
as  dissociation  by  heat. 

10.  Dissociation  by  Solution. — As  heat  may  be  the 
means  of  dissociating  substances,  so  it  is  believed  liquids 
may  be.  When  this  occurs  it  is  called  dissociation  ~by  so- 
lution, or  ionization.  Because  of  the  fact  that  dissocia- 
tion by  solution  permits  of  conductivity  and  the  electroly- 
sis of  the  substance  dissolved,  it  is  often  called  electrolytic 
dissociation,  but  it  must  be  remembered  that  electricity 
has  nothing  to  do  with  the  dissociation.  Further,  since 
in  dissociation  by  this  means  the  particles  formed  are 
able  to  be  attracted  to  the  electrodes  of  an  electric  cir- 
cuit", they  are  believed  to  be  electrically  charged;  hence, 
an  equation  representing  the  results  of  the  dissociation 
of  potassium  chloride  in  water  would  be  thus, 

KC1  ?±  K  +  Cl, 
and  of  zinc  sulphate, 

ZnS04  <=±  Zn  +  S04. 

These  electrically  charged  particles,  whether  atoms  or 
groups  of  atoms,  are  called  ions,  from  a  Greek  word 


242 


APPLIED   CHEMISTRY 


meaning  to  travel.  They  were  so  named  because  of  the 
fact  of  their  constant  movement  from  place  to  place, 
lonization  would  be,  therefore,  the  dissociation  of  a  sub- 
stance into  ions. 

11.  Kind  of  Ions. — Ions  are  either  positive  or  negative 
according  to  whether  they  are  attracted  to  the  cathode  or 
the  anode  in  an  electrolyte.  As  already  indicated,  hydro- 
gen, ammonium  and  the  metals  may  form  positive  ions, 
called  cations  or  cathions,  because  they  are  attracted  by 
the  cathode :  the  nonmetals,  hydroxyl,  and  many  oxygen 
radicals,  like  -S04,  form  negative  ions,  called  anions,  at- 
tracted to  the  anode.  Ions  are  also  spoken  of  as  simple 


Fig.   49. — lonization  of  a  solution   of   common   salt,   and   proof  of  same. 

and  complex.  A  simple  ion  consists  of  a  single  atom,  elec- 
trically charged,  while  a  complex  ion  contains  more  than 
one  atom,  that  is  an  electrically  charged  radical,  like  -HO. 
It  must  be  remembered  that  ions  are  not  atoms.  A  solu- 
tion of  potassium  chloride  abounds  in  chlorine  ions,  but 
it  possesses  none  of  the  properties  of  free  chlorine — no 
color,  no  odor,  no  bleaching  properties.  The  electric 
charge  upon  it,  like  an  efficient  rain  coat  not  only  pre- 
vents its  "solution"  in  water,  as  it  were,  but  also  from 
doing  the  other  things  free  chlorine  would  do.  A  very 
simple  experiment  shows  the  movement  of  the  ions  toward 
the  electrodes  in  a  solution.  If  salt  water,  colored  with 


SOLUTION   AND   IONIZATION  243 

litmus  cubes,  be  put  into  the  U-tube,  as  shown  in  Fig. 
49,  and  the  terminals  of  a  battery  be  inserted,  in  a  very 
short  time  the  blue  color  at  the  anode  will  disappear. 
The  chlorine  ions  have  been  attracted  to  this  arm,  and, 
coming*  in  contact  with  the  positively  charged  carbon  or 
platinum  electrode,  have  lost  the  charge  they  held  by 
having  it  neutralized.  Now,  they  have  become  atoms  of 
free  chlorine.  Immediately,  they  begin  to  bleach  the 
litmus  solution  and  decompose  the  water.  Likewise,  the 
odor  of  fre?  chlorine  becomes  apparent  as  well  as  the 
color,  if  the  process  is  continued  long.  If  the  salt  water 
had  been  colored  by  a  red  litmus  solution  the  anode  arm 
would  have  been  bleached  as  before  while  at  the  cathode 
the  solution  would  have  turned  blue.  The  sodium  ions 
move  toward  the  cathode ;  on  meeting  it  they  give  up 
their  positive  charge  to  the  electrode,  become  atoms  of 
sodium,  and  immediately  begin  to  decompose  the  water 
there.  Thus, 

2Na  +  H20  -»  II,  +  2NaIIO. 

The  hydrogen  escapes  in  bubbles  as  can  easily  be  seen,  and 
the  hydroxyl  ions  of  the  sodium  hydroxide  change  the  red 
litmus  to  blue.  This,  as  has  been  stated  elsewhere,  is 
characteristic  of  all  soluble  hydroxides.  Phenolphthalein 
is  a  coal  tar  product,  which  by  soluble  hydroxides  is 
turned  a  beautiful  violet-red  color.  In  the  above  exper- 
iment, if  a  few  drops  of  an  alcoholic  solution  of  phenol- 
phthalein  be  added  to  the  salt  solution  instead  of  coloring 
with  litmus,  the  solution  at  the  cathode  quickly  turns 
pink,  when  the  current  is  passed,  showing  the  formation 
of  a  hydroxide  just  as  before. 

12.  Ions  and  Valence. — It   will   be   noticed   that   the 

+ 
hydrogen   ion  was  written   above   H   while  that   of  zinc 

+  + 
was    Zn.      It    will   be    found    that    the    electric    charge 


244  APPLIED    CHEMISTRY 

upon  an  ion  is  the  same  as  the  valence.  In  making 
hydrogen,  experimentally,  it  was  found  that  one  atomic 
weight  of  sodium  displaces  one  atomic  weight  of  hydro- 
gen from  water  and  that  one  of  zinc  displaces  two  of 
hydrogen  from  acids.  From  this  it  would  be  seen  that 
the  valence  of  sodium  is  one  and  that  of  zinc  is  two. 

The    ions,   therefore,   would   carry   single    and    double 

+      +  -f 
charges,  respectively,  Na,  Zn. 

13.  Chemical  Action  Ionic.  —  It  has  been  seen  that  a 
piece  of  zinc  dropped  into  pure  dry  hydrogen  chloride 
liquefied,  shows  no  chemical  action,  but  if  water  be 
added  it  becomes  vigorous  immediately.  Likewise,  zinc 
in  concentrated  sulphuric  acid  in  making  hydrogen  gives 
very  indifferent  results.  Ferrous  sulphide  in  concen- 
trated sulphuric  acid  shows  almost  no  chemical  action  at 
all.  In  both  of  the  last  cases  the  addition  of  water 
brings  vigorous  results.  It  is  believed  from  these  and  a 
very  large  number  of  other  experiments,  all  indicating 
the  same  thing,  that  chemical  action  takes  place  between 
ions.  In  terms  of  the  kinetic  theory  the  presence  of  the 
water  results  in  the  ionization  of  the  compounds,  and 
the  ions,  moving  through  the  solution  in  all  directions, 
meet  each  other  and  form  new  combinations.  Thus, 


If  these  two  solutions  are  poured  together  collisions 
between  the  potassium  and  silver  ions  are  impossible, 
because  being  with  like  charge,  as  they  approached  each 
other  repulsion  would  take  place  ;  likewise,  the  chloride 
ion  and  nitrate  ion.  But  collisions  between  potassium 
ions  and  nitrate  ions,  also  between  chloride  and  silver 
ions  could  occur  and  would,  as  well  as  those  indicated 


SOLUTION    AND    IONIZATION  245 

by  the  equations.  But  silver  chloride  is  an  insoluble 
compound,  and  hence  could  not  ionize;  therefore,  as 
fast  as  silver  chloride  formed  it  would  separate  out  from 
the  solution.  Ultimately,  all  the  silver  and  chloride  ions 
would  have  collided  and  been  removed,  at  which  time 
there  would  be  solid  silver  chloride  which  would  be 
in  the  form  of  a  precipitate,  potassium  ions  and  nitrate 
ions,  with  some  molecular  potassium  nitrate. 

14.  Other  Types  of  Reactions. — In  the  case  just  given 
one  of  the  products  is  in  the  form  of  a  precipitate  and 
is  thus  removed  from  the  sphere  of  action.  The  same  is 
true  if  one  of  the  products  is  a  gas.  Thus,  if  lime  water 
is  added  to  a  solution  of  ammonium  chloride,  these 
steps  would  result, 

NH4C1  ?±  NH4  +  Cl, 
Ca(HO)2  i=±  Ca  +  HO  +  HO, 
NH4  +  HO  ^  NIIJIO, 
Ca  +  Cl  +  Cl  ^  CaCL. 

Now  if  the  solution  is  warmed  as  is  done  in  preparing 
ammonia,  the  following  results, 

NH4HO  -»  NH3  +  H,0. 

Ammonia,  being  a  gas,  is  constantly  escaping,  so  that 
the  ammonium  hydroxide  is  being  removed  all  the  time. 
Therefore,  the  ammonium  ions  are  being  removed  and 
the  final  result  is  calcium  chloride  in  water  ionized  as 
shown  by  the  equation, 

Ca  +  Cl  +  Cl<=±CaCl2. 

This  is  typical  of  all  cases  in  which  one  product  is  a  gas. 
There  are  many  others  in  which  all  the  products  are 


246  APPLIED    CHEMISTRY 

soluble  in  water.  Thus,  when  potassium  nitrate  and 
sodium  chloride  are  mixed  in  solution, 

KN03  <F±  K  +  N03, 
NaCl  &  Na  +  Cl. 

Very  shortly  there  would  be  some  potassium  chloride 
molecules  and  some  sodium  nitrate  molecules  from  the  in- 
evitable collisions;  but  these  products  are  both  soluble  in 
water  and  would  both  ionize,  thus, 

KC1  ?±  K  +  Cl, 


Evidently  nothing  is  removed  from  the  sphere  of  action 
in  this  case,  and  when  equilibrium  is  reached,  there  are 
small  amounts  of  all  four  compounds  as  well  as  large 
numbers  of  all  four  ions  shown.  Such  chemical  actions 
do  not  go  to  completion  as  is  the  case  when  one  product 
is  either  a  gas  or  a  precipitate. 

15.  Strong  Bases  and  Strong  Acids.  —  Frequent  use  is 
made  of  the  terms  strong  and  weak  acids  and  bases,  and 
a  clear  understanding  must  be  had.  A  strong  acid  or 
base  is  one  that  is  largely  ionized  in  solution.  Since 
chemical  action  is  between  ions,  where  few  ions  exist  there 
can  be  little  action.  Sulphuric  and  hydrochloric  are 
spoken  of  as  strong  acids;  this  simply  means  that  in 
aqueous  solutions  they  dissociate  so  as  to  produce  a  large 
number  of  hydrogen  ions.  On  the  other  hand,  such  acids 
as  carbonic  and  acetic  .are  regarded  as  weak  acids  for 
the  reason  that  in  solution  they  are  not  ionized  greatly. 
In  concentrations  of  one,  strong  acids  will  be  ionized 
fully  75  per  cent,  while  weak  acids  not  over  one  molecule 
in  something  over  50,000  is  dissociated.  The  same  is  true 
of  bases.  Sodium  hydroxide  dissolved  in  water  is  largely 


SOLUTION    AND    IONIZATION  247 

broken  into  ions  so  that  the  quantity  of  hydroxide  ion 
is  large ;  on  the  other  hand,  eopper  hydroxide  is  a  weak 
base  because  of  the  portion  which  dissolves  only  compara- 
tively few  of  the  molecules  are  ionized. 

Exercises  for  Review 

I.  Define  the  terms  solution,  solvent,  solute. 

-.  Name  seven  kinds  of  solutions  and  give  an  example  of  each. 
What  is  the  most  common  kind? 

3.  What  is  meant  by  a  concentration  of  one  in  a  solution?     Give 
examples. 

4.  What  is  meant  by  a  gram  molecular  weight  of  a  substance? 

5.  Name    three    respects    in   which    a    solution    differs    from    the 
solvent. 

6.  Explain  why  the  specific  gravity  of  a  solution  is  greater  than 
that  of  the  solvent. 

7.  Explain   by    the    kinetic    theory    why    a    solution   has   a   lower 
freezing  point  than  the  solvent.     Why  should  the  boiling  point  be 
raised? 

8.  What  is  meant  by  the  expression,  vapor  pressure  is  lowered? 

9.  What  relation  is  there  between  lowering  of  freezing  point  and 
concentration  of  the  solution? 

10.  If    1   c.c.   of  a  solution  of   sugar   of  concentration   one  con- 
tains a  thousand  molecules,  how  many  would  a  solution  of  glucose 
contain  if  the  concentration  were  the  same? 

II.  What  kind    of   substances  affect  freezing   point   irregularly? 
Why  is  this? 

12.  With  a  concentration  of  one,  how  much  would  a  solution  of 
potassium  chloride  lower  the  freezing  point?  CuSO4?  BaCL?  PtCl4? 

13.  To  prove  that  a  solution  contained  silver  nitrate,  how  many 
tests  would  have  to  be  made?     For  what? 

14.  To  prove  that  a  solution  contained  alcohol,  how  many  tests 
would  be  made?     For  what? 

15.  Why  does  a  solution   of   calcium   chloride,   CaCl2,   not  lower 
the  freezing  point  three  times  1.8,  if  it  is  capable  of  being  broken 
into  three  particles? 

16.  What  is  an  electrolyte?     Name  five.     Name  five  nonelectro- 
lytes. 

17.  Why  are  electrolytes  conductors? 


248  APPLIED    CHEMISTRY 

18.  What  is  meant  by  dissociation?     Illustrate. 

1.9.  Name  two  kinds  of  dissociation.     What  is  ioiiization? 

20.  Define  ion.     Name  four  kinds  with  examples  of  each. 

21.  How  is  an  ion  different  from  an  atom?     Illustrate  with  the 
chloride  ion. 

22.  Give  some  experiment  to  show  that  ions  are  free  to  move. 

23.  If  alcohol  were  put  into  a  U-shaped  tube  and  the  terminals 
of  a  battery  inserted,  what  would  collect  at  the  anode?     Cathode? 

24.  What  relation  is  there  between   ionic  charges  and  valence? 
Illustrate. 

25.  When  chemical  change  takes  place  in  a  solution  between  two 
substances,  explain  what  really  happens. 

26.  Why  does  concentrated  sulphuric  acid  not  react  with  ferrous 
sulphide  ? 

27.  Write  the  ions  formed  by  sulphuric  acid  in  water;  also  fer- 
rous sulphide,  FeS.     Show  by  ionic  equations  what  happens  when 
they  are  put  together. 

28.  Write  the  ionic  equations  showing  what  happens  when  po- 
tassium bromide  and  silver  nitrate  are  put  together  in  a  solution. 

29.  Wrhat  is  meant  by  a  reaction  going  to  completion?     Give  two 
classes  of  reactions  in  which  this  happens. 

30.  Knowing  that  barium  sulphate  is  not  soluble  in  water,  when 
sodium  sulphate,  Na2SO4,  and  barium  chloride,  BaOI.,,  are  put  to- 
gether,  write   the   ionic   equations   and   state   whether   the   reaction 
would  go  to  completion. 

31.  What  is  meant  by  a  strong  acid?   A  strong  base?    Illustrate. 


CHAPTER  XXI 

SULPHUR  AND  COMPOUNDS 

Outline — 

Occurrence  of  Sulphur 
Method  of  Preparation 
Characteristics 

(a)   Physical 

(&)    Chemical 
Uses 
Compounds 

Hydrogen  Sulphide 

The  Oxides 

Sulphurous  Acid 

Sulphuric  Acid 

(«)    Chamber  Process 

(ft)    Contact  Process 

(c)   Characteristics  and  Uses 

Thio sulphuric  Acid 

Sodium  Thiosulphate 

1.  Occurrence  in  Nature. — Sulphur  has  been  known 
from  remote  times.  It  is  found  free  in  abundant  quan- 
tities in  volcanic  regions  such  as  those  of  Sicily.  Near 
the  western  entrance  to  Yellowstone  Park  vast  quanti- 
ties in  a  free  but  impure  form  occur  in  what  are  known 
as  the  Sulphur  Mountains.  In  Louisiana,  at  a  distance 
of  several  hundred  feet  below  the  surface,  are  vast 
amounts  of  nearly  pure  sulphur,  deposited  in  earlier 
ages  probably  through  bacterial  action  upon  sulphur 
compounds.  Gypsum,  calcium  sulphate,  as  well  as  a 
large  variety  of  other  sulphur  compounds,  occur  widely 
distributed,  some  of  which  may  be  used  as  a  source  of 
sulphur. 

249 


250 


APPLIED    CHEMISTRY 


2.  Method  of  Preparation. — At  the  present  time  Louis- 
iana furnishes  by  far  the  greater  part  of  the  sulphur 
needed  by  the  United  States.  The  process  is  very 
similar  to  that  used  for  obtaining  salt  from  underground 
deposits.  Fig.  50  will  make  the  plan  clear.  By  drill- 
ing, a  hole  6  or  8  inches  in  diameter  is  sunk  until  it 
reaches  the  sulphur  deposit.  Four  concentric  pipes  are 
then  inserted;  through  the  two  largest,  water  heated 
under  pressure  to  a  temperature  of  about  170°  C.  is 
run  down  upon  the  sulphur  bed.  Upon  the  innermost 


Fig.    50. — Method   of   obtaining  sulphur   in   Louisiana. 

pipe  pressure  is  secured  by  compressed  air:  in  this  way 
molten  sulphur,  hot  water  and  air  flow  out  through  the 
remaining  pipe  into  large  bins.  Here  the  sulphur  solid- 
ifies while  the  water  is  conducted  away.  The  sulphur 
thus  obtained  is  sufficiently  pure  for  all  uses  except 
those  of  medicine,  and  for  shipment  is  blasted  off  with 
dynamite  and  loaded  into  cars.  Formerly,  about  90 
per  cent  of  the  sulphur  used  in  the  United  States  was 
obtained  from  Sicily.  For  pharmaceutic  preparations 
further  purification  is  deemed  necessary.  The  sulphur 


SULPHUR    AND    COMPOUNDS  251 

is  placed  in  retorts  and  heated  to  the  boiling  point; 
its  vapors  pass  over  into  chambers  where  condensation 
takes  place  upon  the  walls  or  coarse  sacking.  This  is 
in  the  form  of  a  fine  powder,  known  as  flowers  of  sul- 
phur. If  the  process  be  continued  for  considerable  time, 
the  walls  become  sufficiently  warm  to  melt  the  sulphur 
again  and  it  runs  to  the  bottom  and  is  drawn  off  into 
moulds,  in  which  form  it  is  called  brimstone  or  roll  sul- 
pli  ur. 

3.  Physical  Characteristics. — Sulphur  is  a  solid  of 
light  yellow  color.  It  is  not  soluble  in  water  and  is 
without  odor  or  taste.  It  has  a  specific  gravity  about 
twice  that  of  water  and  a  melting  point  about  114.  Its 


Fig.    51. — Sulphur   crystals. 

best  solvent  is  carbon  disulphide  in  which  at  ordinary 
temperatures  about  40  parts  will  dissolve  in  100.  If 
this  solution  be  allowed  to  evaporate  slowly,  as  may  be 
secured  by  tying  two  or  three  thicknesses  of  filter  paper 
over  a  beaker  half  or  two  thirds  filled  with  the  solution,  a 
mass  of  beautiful  crystals  may  be  obtained  such  as  are 
shown  in  Fig.  51.  They  are  of  the  same  'shape  as  those 
found  in  nature  but  usually  somewhat  more  perfect.  They 
are  called  orthorhombic  or  octahedral  crystals.  Sulphur 
also  forms  long,  needle-like  crystals,  known  as  mono- 
clinic.  These  may  be  obtained  by  melting  a  quantity  of 
sulphur  in  a  beaker  or  large  test  tube  and  pouring  upon 
a  filter  paper  in  a  funnel.  In  a  short  time  the  needles 
will  be  seen  growing  rapidly  across  the  surface  of  the 
molten  sulphur.  At  this  stage  the  portion  remaining 


252  APPLIED    CHEMISTRY 

molten  should  be  poured  out,  after  which  the  crystals  may 
be  easily  examined.  The  two  varieties  are  of  the  same 
color,  but  in  many  respects  are  as  dissimilar  as  oxygen 
and  czone.  Monoclinic  sulphur  has  a  specific  gravity  of 
1.96,  while  that  of  the  orthorhcmbic  is  2.06 ;  the  former, 
a  melting  point  of  119,  the  latter  about  114;  below  96° 
C.  the  needles  break  up  into  the  orthorhombic.  Hence, 
while  a  roll  of  sulphur  recently  made  would  consist  of  a 
mass  of  needle-like  crystals  closely  intermingled,  after  a 
time  these  would  have  broken  up  into  small  octahedrons. 
On  the  other  hand,  if  the  orthorhombic  variety  be  heated 
above  96°  C.  but  not  to  the  melting  point,  it  slowly 
changes  into  the  monoclinic  variety.  Sulphur  brought  to 
the  boiling  point  and  cooled  suddenly,  by  pouring  into 
water,  forms  another  variety  known  as  plastic  or  amor- 
phous sulphur.  This  is  very  dark  brown  in  color  and  at 
first  is  soft  and  elastic  and  is  not  soluble  in  carbon  disul- 
phide.  In  a  few  days  it  loses  its  dark  color,  and  becomes 
hard  and  brittle.  It  is  beginning  to  change  back  to  the 
more  liable  variety.  The  process  is  very  slow  and  may 
continim  for  years  without  completion.  If  put  into  water 
and  kept*  at  a  temperature  of  100°  C.  for  about  an  hour, 
the  changa  is  complete.  In  heating  sulphur  to  the  boiling 
point,  it  is  first  a  clear,  golden-yellow,  mobile  liquid.  As 
the  temperature  rises  it  becomes  brownish  in  color,  grow- 
ing gradually  more  viscous  till  it  cannot  be  poured  from 
the  vessel  containing  it.  At  the  boiling  point,  about  448°, 
it  is  again  a  thin  liquid  nearly  black  in  color. 

4.  Chemical  Characteristics.— Sulphur  above  its  kind- 
ling temperature  reacts  easily  with  oxygen,  forming 
the  dioxide.  At  red  tyeat  it  combines  vigorously  with 
both  copper  and  iron  \vith  the  formation  of  sulphides. 
Sulphur  vapor  at  a  temperature  not  far  above  its  boiling 
point  shows  a  density  indicating  a  molecular  formula  of 


SULPHUR    AND    COMPOUNDS  253 

S8 ;  but  like  iodine  and  nitrogen  peroxide,  already  stud- 
ied, as  the  temperature  rises,  the  expansion  of  the  gas 
and  the  specific  gravity  change  much  more  rapidly  than 
justified  by  Charles'  law,  and  at  800°  the  molecular 
weight  indicated  is  about  64,  which  is  that  demanded  if 
the  formula  is  S2.  This  gives  another  illustration  of 
dissociation  by  heat, 

S8  *±  4S, 

5.  Uses  of  Sulphur. — While  no  longer  used  as  exten- 
sively as  formerly  in  medicine,  sulphur  still  enters  into 
a  number  of  pharmaceutic  preparations.  It  is  mildly 
germicidal  and  is  employed  in  some  ointments  for  this 
reason.  It  is  used  extensively  in  viticulture  in  sprays 
to  prevent  the  destructive  effects  of  fungous  diseases  as 
well  as  upon  rose  bushes  for  the  same  reason.  Boiled 
with  lime  it  is  used  upon  peach,  plum  and  other  fruit 
trees  to  prevent  "brown  rot,"  a  disease  of  fungous 
character.  Very  considerable  amounts  are  used  in  the 
manufacture  of  matches,  gunpowder  and  fireworks.  One 
of  the  most  extensive  uses  is  in  the  manufacture  of 
rubber  goods.  Without  the  addition  of  sulphur,  native 
rubber  becomes  unduly  soft  in  warm  weather  and  brittle 
in  cold.  Vulcanite  is  hard  rubber,  obtained  by  heating 
ordinary  rubber  out  of  contact  with  the  air  to  a  consider- 
ably higher  temperature.  This  form  is  familiar  in  pho- 
nograph records,  combs,  telephone  receivers  and  mouth- 
pieces, electric  insulation,  fountain  pens,  and  a  great  va- 
riety of  other  things.  Lampblack  is  added  in  small 
amounts  to  give  a  black  color :  if  pink  is  desired,  vermil- 
ion is  used.  Considerable  sulphur  is  used  in  the  manu- 
facture of  such  compounds  as  carbon  disulphide  and 
sulphur  dioxide.  The  former  is  a  nearly  colorless  liquid 
of  very  unpleasant  odor  as  usually  obtained,  and  em- 
ployed largely  as  a  solvent  for  various  substances. 


254  APPLIED  CHEMISTRY 

6.  Compounds.— Sulphides,— Sulphur  and  oxygen  be- 
ing members  of  the  same  family  show  much  similarity  in 
the  compounds  they  form.     Oxygen  unites  with  all  the 
common    elements    except    fluorine ;    so    sulphur    forms 
compounds  with  all  the  metals  except  gold  and  plati- 
num and  with  a  very  large  number  of  the  nonmetals. 
Nearly   all   the    metals    occur   in    nature    as    sulphides. 

7.  Hydrogen  Sulphide. — In  nature  hydrogen  sulphide 
is  often  found  in  spring  and  artesian  well  waters.    Eggs, 
which  are  proteins  containing  sulphur,  in  decomposing 
produce  quantities  of  hydrogen  sulphide,  familiar  to  all 
in  the   exceedingly  disagreeable,   nauseating   odor.     In 
the  laboratory  it  is  obtained  by  treating   ferrous  sul- 
phide either  with  hydrochloric  or  sulphuric  acid,   con- 
siderably diluted,  thus, 

FeS  +  H2S04  -*  H2S  +  FeS04. 

It  is  a  colorless  gas,  a  little  heavier  than  air,  with  the 
well-known  offensive  odor  of  decomposing  eggs.  It  is 
somewhat  soluble  in  water  with  which  it  forms  an  acid 
solution,  hydrosulpkuric  acid.  It  may  be  liquefied  at 
about  -60°.  Hydrogen  sulphide  burns  with  a  pale-blue, 
hot  flame  with  the  characteristic  odor  of  burning  sulphur. 
The  equation  is 

2H2S  +  302   ->  2H20  +  2S02. 

If  a  cold  dish  be  held  against  the  flame,  a  deposit  of  sul- 
phur is  formed.  This  shows  that  by  the  heat  present  the 
escaping  hydrogen  sulphide  is  dissociated  to  a  greater  or 
less  extent,  thus, 

2H2S  *±  2H2  +  S2. 

It  is  a  very  poisonous  gas,  producing  dizziness,  uncon- 
sciousness, and  ultimately  death.  However,  as  at  least 


SULPHUR   AND    COMPOUNDS  255 

1/2  of  1  per  cent  is  necessary  for  fatal  results,  and  as  very 
much  smaller  proportions  than  this  are  distinctly  notice- 
able on  account  of  its  very  strong  odor,  serious  results 
very  rarely  occur.  It  is  said  that  very  dilute  chlorine, 
obtained  by  adding'  hydrochloric  acid  to  bleaching  pow- 
der solution,  is  the  best  antidote.  It  must  be  remembered, 
however,  that  chlorine  is  more  poisonous  than  hydrogen 
sulphide ;  hence,  when  used  as  an  antidote,  great  care 
must  be  exercised.  Like  carbon  and  carbon  monoxide, 
hydrogen  sulphide  is  a  reducing  agent.  Hence,  when 
bubbled  through  strong  sulphuric  acid,  partial  reduction 
of  the  acid  results  with  the  formation  of  sulphur  dioxide, 
thus, 

H2S04  +  H2S  -»  S  +  S02  +  2H20. 

Hydrogen  sulphide,  therefore,  cannot  be  dried  by  this 
method.  Brought  into  contact  with  sulphur  dioxide,  a 
similar  reduction  takes  place  with  the  precipitation  of 
free  sulphur,  thus, 

2H2S-f  S02  -»  2H20  +  3S. 

This  probably  accounts  in  part  at  least  for  the  deposits  of 
sulphur  in  volcanic  regions,  as  both  the  sulphide  and 
oxide  are  produced  by  the  action  of  heat  upon  compounds 
present  in  the  earth. 

Dissolved  in  natural  water,  artesian  or  spring,  hydro- 
gen sulphide  is  supposed  to  have  therapeutic  value,  but 
this  is  very  doubtful.  In  the  laboratory,  however,  it  is 
indispensable.  It  serves  as  the  means  of  separating  a 
large  number  of  the  metals  into  groups  as  the  starting 
point  of  most  chemical  analyses. 

8.  Sulphur  Dioxide. — There  are  two  oxides,  sulphur 
dioxide  and  trioxide,  but  the  former  is  the  more  com- 
mon. It  is  produced  when  either  sulphur  or  hydrogen 
sulphide  is  burned  in  the  air.  In  the  laboratory  it  is 


256  APPLIED    CHEMISTRY 

generally  prepared  by  treating  copper  turnings  or  bits 
of  charcoal  with  concentrated  sulphuric  acid,  heated 
cautiously  but  somewhat  strongly.  It  might  be  sup- 
posed at  first  thought  that  copper  added  to  sulphuric 
acid  would  cause  an  evolution  of  hydrogen  as  zinc  did. 
It  will  be  found,  however,  by  referring  to  Fig.  14  on 
p.  65  that  copper  is  less  strongly  electropositive  than 
is  hydrogen,  hence  could  not  displace  the  latter  from  an 
acid.  Moreover,  we  have  seen  that  concentrated  sul- 
phuric as  used  in  this  case  gives  but  few  hydrogen  ions, 
and  as  chemical  changes  are  usually  between  ions,  a  re- 
action similar  to  that  between  zinc  and  dilute  sulphuric 
acid  could  not  be  expected  here.  Thus  with  zinc  we  had 

Zn  +  H2SO4  -»  H2  +  ZnS04. 

Concentrated  sulphuric  acid,  when  heated,  is  an  oxidiz- 
ing agent,  that  is,  it  gives  Up  a  part  of  its  oxygen;  in 
other  words,  in  the  present  case  the  copper  serves  as 
a  reducing  agent  in  its  reaction  with  sulphuric  acid. 
It  is  not  possible  to  prove  that  a  certan  chemical  reac- 
tion takes  place  by  steps,  still  it  is  entirely  possible 
that  in  this  case  as  in  many  others,  such  is  true.  On 
the  above  supposition,  the  first  step  in  the  reaction  would 
be  shown  by  the  equation, 

Cu  +  H2S04  ->  CuO  +  H20  +  S02. 

Then,  secondly,       CuO  +  H2S04  ->  CuS04  +  H20. 
Adding  the  two  equations  gives  the  final  result  as  it  is 
known  to  be, 

Cu  +  2H2S04  ->  CuS04  +  2H20  +  S02. 

9.  Characteristics  of  Sulphur  Dioxide. — Sulphur  diox- 
ide is  a  colorless  gas  with  a  very  suffocating  odor.  It 
is  one  of  the  easiest  gases  to  liquefy;  this  may  be  ac- 
complished in  any  laboratory  by  surrounding  a  spiral 


SULPHUR    AND    COMPOUNDS  257 

tube  connected  with  the  sulphur  dioxide  generator  with 
a  freezing  mixture  of  ice  and  salt.  The  liquid  may  be 
kept  sealed  hermetically  in  glass  tubes,  as  the  pressure 
at  ordinary  temperatures  is  only  about  three  and  a  half 
atmospheres.  The  liquid  if  pure  is  nearly  colorless, 
like  water,  and  boils  at  -8°  C.  The  gas  is  soluble  in 
water  to  the  extent  of  about  fifty  volumes  in  one  and 
forms  the  unstable  sulphurous  acid,  H2S03, 


It  has  a  density  compared  to  hydrogen  of  32,  hence  is 
nearly  two  and  a  half  times  as  heavy  as  air.  Being  an 
unsaturated  compound,  since  the  valence  of  sulphur  is 
six,  it  has  the  power  of  taking  up  another  atomic  weight 
of  oxygen  for  each  molecule,  and  thus  forms  sulphur  tri- 
oxide. 

10.  Uses  of  Sulphur  Dioxide.  —  Until  comparatively  re- 
cent years  sulphur  dioxide  was  used  for  disinfecting 
public  buildings  and  homes  in  case  of  contagious  dis- 
eases. The  gas  was  secured  by  burning  sulphur  "can- 
dles" in  the  various  rooms  or  where  the  ventilating  fans 
would  carry  it  to  all  parts  of  the  building.  As  formalde- 
hyde is  much  more  effective  and  more  easily  obtained 
it  is  largely  supplanting  sulphur  dioxide  for  fumigating 
purposes.  It  is  used  extensively  for  bleaching  various 
food  products,  as,  for  example,  glucose  syrups,  already 
mentioned  ;  also,  for  freshly  cut  fruits  in  drying.  The 
fruit  is  peeled,  cored  and  sliced,  by  machine  at  a  single 
operation,  and  the  slices  spread  upon  trays  over  a  fur- 
nace in  an  evaporator.  A  teaspoonful  of  sulphur  is 
put  into  a  cup  on  top  of  the  furnace  each  time  a  double 
tray  of  fruit  is  inserted.  The  sulphur  burns,  forming 
sulphur  dioxide,  and  the  gas  flows  up  over  the  fruit.  No 
brown  discoloration  occurs  as  would  be  the  case  in  pure 


258  APPLIED    CHEMISTRY 

air,  and  in  a  very  few  minutes  the  fruit  is  dry  upon 
the  surface  after  which  it  remains  perfectly  white.  In 
many  localities  in  the  West,  fruits,  especially  peaches 
and  apricots,  are  dried  in  the  sun.  To  prevent  attack 
by  ants  and  other  insects,  the  fruit  after  being  cut  is 
taken  to  a  "sulphuring"  room  where  it  is  exposed  to 
sulphur  dioxide  fumes  for  a  time.  Sufficient  is  absorbed 
to  protect  the  fruit  in  drying ;  however,  at  the  tempera- 
ture present,  as  the  water  evaporates,  the  sulphur  diox- 
ide, except  in  minute  traces,  also  disappears,  so  that  no 
harmful  results  follow.  The  bleaching  of  English  wal- 
nuts and  almonds,  possibly  of  some  other  nuts  in  Califor- 
nia, is  a  common  practice.  Lying  upon  the  ground  in 
the  "hulls"  as  they  may  for  some  days  before  being 
gathered,  the  white  shells  become  stained  or  mildewed, 
so  that  when  finally  shelled  and  dried  they  are  of  vary- 
ing shades  of  brown  and  gray.  When  taken  to  the 
packing  houses,  after  being  assorted  into  sizes,  they  are 
passed  through  a  solution  of  bleaching  powder  to  which 
dilute  hydrochloric  acid  has  been  added,  then  carried 
by  elevators  to  a  "sulphuring"  room,  where  they  are 
exposed  for  some  time  to  the  fumes  of  sulphur  dioxide. 
The  result  is  a  product  with  shells  of  a  uniformly 
creamy-white  color.  They  are  thus  rendered  pleasing 
in  appearance  without  detracting  from  the  wholesome 
character  of  the  nuts. 

Liquefied  sulphur  dioxide  is  now  an  article  of  com- 
merce and  is  used  extensively  for  bleaching  woolens, 
straws  and  silks.  Naturally,  these  articles  are  all  of 
varying  shades  of  yellow  and  woven  thus  are  unattrac- 
tive in  appearance.  Chlorine  is  destructive  of  all  such 
and  cannot  be  used.  Sometimes  hydrogen  peroxide  is 
employed,  but  it  is  not  so  satisfactory  as  sulphur  di- 
oxide. What  the  chemical  action  is  when  bleaching  is 


SULPHUR    AND    COMPOUNDS  259 

done  with  this  gas  is  uncertain.  The  other  two  bleaching 
agents  already  studied  undoubtedly  act  by  oxidation.  As 
sulphur  dioxide  is  an  unsaturated  compound  it  would 
presumably  act  by  reduction  of  the  colored  compounds 
in  the  fabric  to  colorless.  All  such  articles,  on  exposure 
to  air  and  sunlight,  again  become  yellow,  caused  possi- 
bly by  their  again  taking  up  oxygen  and  returning  to 
their  first  condition.  Iceless  refrigerators  kept  cold  by 
the  evaporation  of  liquid  sulphur  dioxide  are  now  being 
installed  in  many  homes.  The  principle  is  the  same  as 
already  explained  in  the  manufacture  of  ice. 

11.  Sulphur  Trioxide.—  This  oxide  has  little  interest 
outside  the  fact  that  it  is  the  anhydride  of  sulphuric 
acid.    It  will  be  taken  up  in  connection  with  the  prepara- 
tion of  that  acid. 

12.  Sulphurous  Acid.  —  As  already  stated  this  acid  is 
formed  when  sulphur  dioxide  is  passed  into  wrater.    It  is 
unstable  and  of  little  importance. 

13.  Sulphuric  Acid.  —  Under  the  name,   oil  of  vitriol, 
sulphuric   acid  has   been   known   for   centuries.     It   was 
formerly  made,   somewhat  impure,  by  distilling  ferrous 
sulphate,  called  green  vitriol,  which  gave  the  name  to  the 
acid.     At  the  present  time  two  methods  are  used  in  its 
manufacture,  the  chamber  and  the  contact  process.     The 
former  is  the  older  method,  but  the  latter,  where  it  may  be 
applied   is  the   cheaper.     Both   employ   sulphur   dioxide 
as  the  starting  point. 

14.  The  Chamber  Process.  —  By  this  method  the  sul- 
phur  dioxide   needed   is   usually   obtained   by   roasting 
iron  pyrite,  FeS2,  which  reacts  with  the  oxygen  of  the 
air  thus, 

4FeS2  hll02  ->  8S02  +  2Fe203- 


The  gas  is  passed  into  large  chambers  where  it  meets 


260  APPLIED   CHEMISTRY 

nitric  acid  vapors  prepared  by  the  action  of  sulphuric 
acid  upon  sodium  nitrate,  thus, 

2NaN03  +  H2S04  -»  2HN03  +  Na2S04. 

The  nitric  acid  and  the  sulphur  dioxide  react,  with  the 
formation  of  sulphur  trioxide  and  one  or  more  nitrogen 
oxides, 

2HN03  +  3S02  ->  3S03  +  H20  +  2NO. 

Steam  and  currents  of  air  are  also  introduced  by  which 
the  sulphur  trioxide  forms  sulphuric  acid  and  the  nitric 
oxide  becomes  peroxide,  thus, 

H20  +  S03  -»  H2S04, 
2NO  +  02  ->  2N02. 

Only  small  quantities  of  nitric  acid  are  needed,  since  it 
serves  merely  as  a  catalytic  agent  to  transfer  the  oxy- 
gen from  the  air  to  the  sulphur  dioxide.  However,  as 
four-fifths  of  the  air  is  nitrogen  which  has  no  use  in  this 
process,  in  removing  it  special  plans  must  be  adopted 
to  prevent  loss  of  the  nitrogen  oxides  also.  The  es- 
caping gases  are  made  to  pass  up  through  what  is  called 
the  Gay-L/ussac  tower,  little  more  than  a  chimney  with 
a  lattice  work  of  brick  or  tile,  over  which  sulphuric 
acid  slowly  trickles.  This  acid  has  the  power  of  com- 
bining with  the  nitrogen  oxide  present  but  not  with  the 
nitrogen,  and  forms  what  is  called  nitre  acid  or  nitrosyl 
sulphuric  acid.  Thus,  little  of  the  nitric  oxide  is  lost. 
The  nitrosyl  sulphuric  is  then  pumped  up  to  the  top  of 
another  chimney  known  as  the  Glover  tower  and  trickling 
down  there  meets  the  steam  and  fresh  supplies  of  sulphur 
dioxide.  The  steam  decomposes  the  niter  acid  forming 
sulphuric  and  sets  free  the  nitric  oxide  which  again  com- 
bines with  the  oxygen  of  the  air;  hence  the  process  be- 
comes continuous.  The  chambers  where  the  acid  is  pro- 


SULPHUR    AND    COMPOUNDS 


261 


duced  are  lined  with  lead,  since  it  is  not  attacked  by  di- 
lute sulphuric.  When  it  reaches  a  strength  at  which  it 
begins  to  react  with  the  lead,  it  is  removed  and  further 
concentrated  in  stills  made  of  cast  iron  or  platinum. 
(See  Fig.  52.) 

15.  The  Contact  Process. — This  process  uses  platinum 
as  the  catalytic  agent.  It  is  found  that  sulphur  dioxide 
and  air,  mixed  and  passed  through  a  heated  tube,  do 
not  react  to  any  appreciable  extent.  If  finely  divided 


HUer  Pot  S      Pyritet  Burners 


Fig.  52. — Chamber  process  for  sulphuric  acid.  The  escaping  gases  pass 
up  the  Gay-Lussac  tower  where  they  meet  the  streams  of  sulphuric  acid. 
This  combines  with  the  nitrogen  oxide  present,  forming  the  niter  acid,  so 
called.  This  is  pumped  to  the  top  of  the  Glover  tower,  where,  descending, 
it  meets  the  steam,  which  decomposes  it.  The  nitrogen  oxide  then  begins  its 
work  all  over  again. 

platinum  be  present,  however,  the  union  is  rapid.  In 
preparing  the  catalyzer,  asbestos  is  dipped  into  a  solu- 
tion of  platinum  chloride  and  heated.  The  chlorine  is 
expelled  and  the  finely  divided  platinum  is  left  adher- 
ing to  the  surface  of  the  asbestos.  When  this  is  heated 
and  the  mixed  air  and  sulphur  dioxide  passed  through 
it,  sulphur  trioxide  is  formed,  which  though  a  solid, 
is  vaporized  by  the  heat  present  and  passes  out  of  the 


262  APPLIED    CHEMISTRY 

catalyzer  into  a  receiver  containing  moderately  dilute 
sulphuric  acid,  such  as  is  obtained  by  the  chamber  proc- 
ess. This  continues  till  the  liquid  becomes  a  white 
crystalline  solid,  known  as  fuming  sulphuric  acid,  with 
the  formula,  H2S207,  or  H2S04.S03.  This  indicates  it  is 
sulphuric  acid  saturated  with  the  anhydride,  sulphur 
trioxide.  It  might  be  supposed  that  the  sulphur  triox- 
ide  obtained  by  the  contact  process  would  be  passed 
directly  into  water,  rather  than  into  dilute  sulphuric 
acid.  The  reason  that  this  is  not  done  is  that  the  reac- 
tion is  so  violent  that  the  heat  produced  volatilizes  con- 
siderable portions  of  the  trioxide  with  much  loss. 

16.  Characteristics  of  Sulphuric  Acid. — When  pure, 
sulphuric  acid  is  a  colorless,  oily  liquid,  with  a  specific 
gravity  of  1.84.  It  boils  at  330°  C.,  but  considerable 
portions  are  broken  up  into  sulphur  trioxide  and  water, 
thus, 

H2S04  *±  S03  +  H20. 

Sulphuric  acid  is  strongly  hygroscopic  and  exposed  to 
the  air  rapidly  increases  in  volume  with  corresponding 
dilution.  When  water  is  added,  great  heat  is  produced; 
hence,  it  is  never  safe  to  pour  water  into  the  concen- 
trated acid.  The  reverse  order  should  always  be  fol- 
lowed. As  already  seen,  this  strong  attraction  for  water 
is  made  use  of  in  drying  gases.  When  a  pine  splinter  is 
dipped  into  concentrated  sulphuric  acid,  it  is  charred, 
as  is  also  a  lump  of  sugar.  From  the  former,  being 
largely  cellulose,  CGH1005  the  acid  removes  the  hydrogen 
and  oxygen  as  if  it  were  water,  leaving  the  carbon  be- 
hind. The  same  is  true  of  the  sugar.  In  the  diluted 
form  sulphuric  acid  is  largely  ionized,  hence  is  a  good 
conductor  of  electricity,  and  with  any  metal  more  pos- 
itive than  hydrogen  readily  reacts,  giving  off  the  hydro- 
gen. In  concentrated  form  there  are  very  few  ions  pres- 


SULPHUR   AND    COMPOUNDS  263 

ent;   it  is  then  a   very  poor   conductor  and   with   such 
metals  as  zinc  and  iron  its  reaction  is  very  slight. 

17.  Uses. — This  is  the  most  extensively  employed  of 
all  acids.    It  is  used  in  the  preparation  of  all  other  acids ; 
the  method  for  hydrochloric  and  nitric  AVC  have  already 
seen.     It  is  used  in  the  manufacture  of  explosives  such 
as  nitroglycerine  and  guncotton,  for  the  preparation  of 
fertilizers  from  native  phosphate  rocks,  in  refining  oils 
derived  from  petroleum  and  in  the  preparation  of  coal 
tar  dyes. 

18.  Thiosulphuric   Acid. — This    acid   has   never   been 
prepared  but  its  salts  are  well  known.     It  has  the  for- 
mula, H2S20.5,  which  will  be  seen  to  be  sulphuric  with 
one  of  the  atoms  of  oxygen  replaced  by  one  of  sulphur. 
The  first  part  of  the  word,  thio,  is  from  the  Greek  word 
for  sulphur,  and  is  given  to  this  acid  to  indicate  the  fact 
of  the  substitution  of  the  sulphur  for  the  oxygen.     One 
salt  of  this  acid,  sodium  thiosulphate,  is  very  important. 
It  is  sold  under  the  name  "hypo,"  formerly  erroneously 
called  hyposulphite   of  soda.     It  is  used  extensively   in 
photography  in  "fixing"  plates  and  prints  so  that  they 
will  not  be  further  acted  upon  by  the  light.     It  is  also 
used  as  an  antichlor  in  the  bleaching  of  textile  fabrics  to 
remove  the  last  traces  of  the  chlorine,  so  as  to  prevent  its 
attacking  the  cloth.    The  fact  that  it  was  used  during  the 
later  part  of  the  war  in  gas  masks  has  been  mentioned 
elsewhere. 

Exercises  for  Review 

1.  Name  three  localities  where  sulphur  is  found  very  abundantly. 
In  what  condition  is  it  and  how  situated? 

2.  Give  the  method  of  obtaining  the  supply  used  in  the  United 
States. 

P>.  Name  four  varieties  of  sulphur  and  state  how  each  may  be 
obtained. 


264  APPLIED    CHEMISTRY 

4.  Give  some  important  differences  between  the  two  crystalline 
varieties. 

5.  Give  the  chief  physical  characteristics  of  sulphur.     How  does 
the  amorphous  differ  from  the  yellow? 

6.  What  is  an  allotrope?     What  other  substances  have  we  met 
with  in  allotropic  forms? 

7.  Give  the  chief  chemical  characteristics  of  sulphur. 

8.  Give  some  very  important  uses  of  sulphur.     What  is  vulcan- 
ite?    Uses. 

9.  Where  is  hydrogen  sulphide  found  in  nature?     Give  some  of 
its  properties. 

10.  Write  the  equation  showing  the  combustion  of  hydrogen  sul- 
phide.    Why  cannot  it  be  dried  by  sulphuric  acid  as  many  gases 
are? 

11.  What  is  meant  by  reduction?     When  hydrogen  sulphide  and 
sulphur  dioxide  are  mixed,  which  is  reduced,  which  is  oxidized?     Is 
it  possible  to  reduce  one  substance  without  oxidizing  another. 

12.  Name  the  oxides  of  sulphur  and  give  their  formulas. 

13.  How  is  sulphur   dioxide  prepared  in  the  laboratory?     How 
for   fumigating?     Why   is   hydrogen   not   obtained   from   the   sul- 
phuric  acid   by   copper? 

14.  Give  the  chief  properties  of  sulphur  dioxide. 

15.  Name  the  most  important  uses  of  sulphur  dioxide. 

16.  Name   two   other  bleaching  agents   previously   studied.     For 
\»hat  are  they  used  to  bleach? 

17.  Give  the  names  of  two  processes  for  making  sulphuric  acid. 
How  did  it  come  to  be  called  "oil  of  vitriol"? 

18.  Describe  briefly  the  chamber  process  and  write  the  equations. 

19.  Describe  briefly  the  contact  process.     What  is  the  catalytic 
agent  in  each  process? 

20.  Describe   the   sulphuric  acid  and  give  some  important  uses. 

21.  Why   does  a  lump   of   sugar  in  concentrated  sulphuric  acid 
turn  black? 

22.  What  is  the  action  of  sulphuric  acid  in  making   nitrocellu- 
lose? 

23.  For  what  is  hypo  used?     What  is  its  chemical  name? 


CHAPTER  XXII 

PERIODIC   CLASSIFICATION   OF   ELEMENTS 

Outline — 

Comparison  of  Metals  and  Nonmetals 

Atomic  Weight  and  Chemical  Characteristics 

The  Periodic  Table 

Valence  in  the  Table 

Relation  of  the  Properties  to  Position  in  Table 

Group  Characteristics 

Numerical  Relations 

Characteristics  of  Compounds  as  Related  to  Position 

1.  Classification  of  the  Elements. — Heretofore  we  have 
spoken  of  the  elements  as  metals  and  nonmetals.  Most 
of  the  common  metals  are  of  considerable  density  and 
lustrous;  but  sodium  and  potassium  are  both  so  light 
as  to  float  on  water,  yet  are  decidedly  metallic  in  char- 
acteristics. Arsenic  has  a  bright,  metallic  luster,  yet 
can  hardly  be  called  a  true  metal.  We  have  spoken  of 
the  metals  as  forming  electropositive  ions  and  the  non- 
metals,  electronegative:  in  a  general  way  this  is  true,  yet 
many  of  the  metals  are  found  in  complex  electronegative 
ions.  Aluminum  and  tin  are  both  metals,  yet  well  known 
salts  exist  in  which  with  oxygen  these  metals  constitute 
the  negative  ion.  Likewise  some  nonmetals  may  form 
positive  ions.  The  metals  have  been  spoken  of  as  form- 
ing basic  oxides  and  the  nonmetals  as  anhydrides.  Gen- 
erally speaking,  this  is  true.  However,  zinc  hydroxide, 
Zn(HO)2,  and  aluminum  hydroxide,  A1(HO)3,  are  both 
soluble  in  sodium  hydroxide,  which  indicates  that  the 
two  bases  must  have  ionized  as  if  they  were  acids,  thus, 

265 


266  APPLIED    CHEMISTRY 

H2Zn02  *±  HH  +  Zn02, 


H3A103  ^±  HHH  +  A103. 

This  must  be  true  for  the  salts  formed  are  Na2Zn02  and 
Na3A103,  sodium  zincate  and  sodium  aluminate.  It  is 
seen,  therefore,  that  there  are  many  exceptions  to  the 
general  statements  regarding  the  two  divisions  of  ele- 
ments hitherto  used,  such  that  this  method  of  classifi- 
cation is  far  from  satisfactory. 

2.  Classification  by  Atomic  Weights.  —  For  long  years 
there  have  been  chemists  who  believed  that  the  charac- 
teristics of  an  element  bore  some  close  relation  to  and  are 
dependent  upon  its  atomic  weight.  Various  attempts 
were  made  to  show  this,  but  too  many  facts  were  un- 
known for  any  marked  success.  It  remained  for  a  great 
Russian  chemist  who  died  in  1907,  to  prepare  what  is 
known  as  the  "Periodic  Table"  and  to  present  the 
"Periodic  System"  in  such  a  way  as  to  cause  its  ac- 
ceptance by  chemists  at  large.  Starting  with  the  idea 
that  the  properties  of  an  element  are  a  function  of  the 
atomic  weight,  Mendeleeff  arranged  the  elements  in  the 
order  of  their  atomic  weights,  beginning  with  the  light- 
est, but  omitting  hydrogen.  In  this  way  he  had  lithium, 
glucinum,  boron,  carbon,  nitrogen,  oxygen,  fluorine, 
sodium,  magnesium,  aluminum,  silicon,  phosphorus,  sul- 
phur, chlorine,  potassium,  calcium,  and  so  on.  By  in- 
specting this  arrangement  he  discovered  that  leaving 
lithium,  there  is  no  other  element  similar  to  it  until 
sodium  is  reached  in  the  eighth  space  beyond,  and  then 
potassium  another  octave  beyond  the  sodium.  Starting 
with  fluorine,  no  other  element  is  met  similar  to  it  until 
chlorine  is  reached,  the  eighth  beyond.  Observing  this 
fact  in  many  instances,  he  next  attempted  to  arrange  the 
elements  known  to  him  into  octaves,  putting  like  elements 


PERIODIC    CLASSIFICATION    OF    ELEMENTS  267 

under  each  other.  To  make  the  elements  known  at  that 
time  agree  with  his  theory,  he  was  compelled  to  leave 
many  spaces  in  the  table  he  prepared  blank.  But  in  doing 
so  he  predicted  these  spaces  would  be  filled  in  the  years 
to  come ;  what  is  more,  he  even  foretold  the  general  prop- 
erties these  unknown  elements  would  possess,  their  ap- 
proximate atomic  weights,  and,  in  some  instances,  actually 
suggested  names  for  them.  Most  of  his  predictions  have 
since  that  time  been  fulfilled,  although  the  names  he  sug- 
gested have  not  been  accepted.  The  latest  form  of  the  ta- 
ble, with  some  omissions  as  noted,  as  well  as  of  some" 
very  rare  elements  whose  position  as  yet  is  not  deter- 
mined, is  given  on  page  268. 

Only  a  very  brief  study  of  the  table  is  possible  at  this 
time,  but  some  knowledge  of  it  is  necessary  and  will  be 
found  very  helpful  to  the  student.  Let  it  be  remembered 
that  the  basis  of  arrangement  is  the  atomic  weights  of  the 
elements. 

3.  Valence  in  the  Table. — The  vertical  divisions  in  the 
table  are  called  Groups  and  the  horizontal  divisions,  Pe- 
riods. By  looking  at  the  top  of  each  group,  beginning 
with  lithium,  it  will  be  seen  that  the  valence  increases 
from  one  up  to  seven.  This  is  true  for  each  period,  with 
few  exceptions  which  will  be  noticed.  It  is  based  upon  the 
oxides  which  the  elements  form.  For  example,  taking 
the  second  period,  the  respective  oxides  have  the  formu- 
las, Na20,  MgO,  A1203,  SiO2,  P205,  S03,  CL07.  The 
next  period,  if  the  oxides  are  taken,  shows  the  same  va- 
lence, and  so  on  through  the  table.  If  the  hydrogen  com- 
pounds are  considered  after  the  carbon  group  is  passed,  in 
which  the  valence  is  four,  the  apparent  value  decreases 
by  one  at  each  group.  Thus,  we  have  the  formulas  for 
the  four  compounds,  marsh  gas,  ammonia,  water  and  hy- 
drogen chloride,  H4C,  H8N,  H20?  HC1.  The  following 


268 


APPLIED    CHEMISTRY 


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PERIODIC    CLASSIFICATION    OF   ELEMENTS  269 

periods  show  like  valence  with  the  hydrogen  compounds. 
When  M'endeleeff  first  prepared  the  table  no  element  of 
the  first  column  had  been  discovered  and  he  made  no 
plans  for  any  such  group.  But  strange  to  say,  and  won- 
derfully strengthening  the  probable  truth  underlying  his 
plan,  when  the  argon  group  was  discovered  one  by  one, 
with  a  slight  exception  to  be  noted,  they  all  fitted  into 
the  general  plan  and  no  changes  had  to  be  made.  Singu- 
larly, too,  their  valence  is  zero,  that  is  they  have  no  power 
of  combining  with  other  elements  and  as  far  as  discovered 
form  no  compounds  whatever.  The  slight  exception  to 
be  noted  is  that  argon  as  thus  far  prepared  is  slightly 
heavier  than  potassium,  whereas  it  should  be  lighter.  The 
probable  explanation  is  that  the  argon  thus  far  obtained 
is  not  pure  but  contains  small  quantities  of  one  or  more 
of  the  heavier  gases  belonging  to  the  same  group.  It  will 
be  remembered  that  for  years  this  was  found  true  of  the 
nitrogen  obtained  from  the  air ;  and  the  fact  of  its  un- 
seeming  density  when  thus  prepared  led  to  the  discovery 
of  argon.  One  other  exception  which  might  be  mentioned 
here  is  that  iodine  is  slightly  lighter  than  tellurium, 
whereas  the  reverse  should  be  true.  It  is  generally  be- 
lieved that  the  weight  of  the  iodine  will  sometimes  be 
found  to  be  slightly  incorrect.  Constant  efforts  are  be- 
ing made  to  ascertain  whether  this  may  not  be  true. 

4.  Position  of  the  Elements  and  Properties. — It  will 
be  found  that  as  we  go  from  left  to  right  in  the  table, 
omitting  always  the  argon  group,  the  elements  become 
less  and  less  electropositive  and  passing  the  carbon 
group,  become  more  and  more  negative.  Thus,  sodium 
is  very  strongly  positive  while  chlorine  is  equally 
strongly  negative.  Sodium  forms  a  very  strong  base, 
chlorine  a  very  strong  acid.  Taking  the  right  hand 
end  of  the  table  it  will  be  found,  as  we  go  down  the 


270  APPLIED    CHEMISTRY 

group,  that  with  the  increasing  weight  the  elements 
become  less  and  less  acidic  in  properties  and  begin  to 
have  some  of  the  physical  properties  of  the  metals. 
Thus,  in  the  halogen  group,  iodine  is  solid  in  form  and 
has  a  luster,  closely  resembling  that  of  most  metals.  In 
the  nitrogen  family  the  lightest  one  is  a  gas,  phosphorus 
is  a  waxy  solid,  arsenic  a  brittle  solid,  but  lustrous, 
antimony  decidedly  metallic  in  appearance  but  with 
some  chemical  properties  of  an  acidic  element,  while  bis- 
muth, the  heaviest,  is  a  metal  both  in  appearance  and 
behavior.  Hence,  instead  of  dividing  the  table  into 
positive  and  negative  elements  by  a  vertical  line  near 
the  center,  it  must  be  done  by  an  irregular,  or  zigzag 
diagonal,  starting  at  the  left  of  boron,  leaving  it  above 
and  aluminum  below  the  line,  and  so  on  through,  leaving 
iodine  above.  Divided  in  this  way  the  elements  above 
the  line  generally  speaking  are  electronegative  or  acid 
forming  elements,  while  those  below  are  positive  or  base 
forming  elements.  However,  it  must  be  further  noted, 
that  the  elements  near  the  irregular  diagonal  usually 
partake  of  a  dual  character  and  form  both  acids  and 
bases,  though  weak  ones.  Thus  aluminum,  arsenic,  an- 
timony, tin  and  others  less  familiar  to  the  student  all 
serve  both  as  acid-  and  base-forming  elements  at  dif- 
ferent times. 

5.  Group  Characteristics. — Taking  any  particular 
group  for  study  it  is  found  that  all  the  members  possess 
the  same  general  characteristics  and  form  similar  com- 
pounds. We  have  thus  noticed  two  members  of  the 
sodium  group.  Both  are  silvery  white  metals,  light 
enough  to  float  on  water,  decompose  it  readily  even  in 
the  cold,  are  strongly  caustic  and  form  strong  hydrox- 
ides. Taking  the  chlorine  group,  it  is  found  that  they 
resemble  each  other  equally  strongly.  SQ  ^  it  is  foun4 


PERIODIC    CLASSIFICATION    OF   ELEMENTS  271 

largely  true  throughout.  Most  strikingly  is  this  ob- 
served in  the  chemical  behavior  and  in  the  compounds 
formed.  Thus,  the  sodium  group  forms  no  ordinary 
compounds  of  hydrogen  for  the  reason  that  they  are  all 
strongly  positive  as  is  hydrogen  also,  but  they  do  form 
oxides  of  the  type,  Na20.  The  halogens  form  acids 
after  the  type,  HC1.  The  sulphur  group  forms  com- 
pounds with  hydrogen  seen  in  the  formulas,  H20,  H2S, 
H2Se,  H2Te  and  with  the  oxides  whose  formulas  are  S03, 
Se03,  Te03.  The  nitrogen  family  forms  hydrogen  com- 
pounds shown  in  the  formulas,  NH3,  PH3,  AsH3,  SbH3 
and  oxide  compounds  in  N205,  P205,  As205,  Sb20r>,  Bi205. 
Hence,  having  learned  the  characteristics  and  com- 
pounds of  one  member  of  a  group,  we  may  know,  in  a 
measure  that  the  same  things  are  true  of  other  members 
of  the  same  group. 

6.  Numerical  Relations. — It  was  stated  that  Mende- 
leeff  predicted  with  approximate   accuracy  the  atomic 
weights  of  the  unknown  elements.     By  observation  it 
will  be  seen  that  the  atomic  weight  of  any  element  is 
roughly  speaking  the  arithmetic  mean  of  those  of  the  two 
adjacent  elements.     To  illustrate:    Sodium,  weight  23, 
is  one-half  the  sum  of  7  and  39,  the  weights  of  lithium 
and  potassium;  scandium,  weight  44,  is  half  the  weight 
of   calcium   and   titanium,   40   and   48.      Thus   it   is   all 
through  the  table,  although  not  always  as  exact  as  in 
these  two  cases ;  but  the  variation  is  not  great. 

7.  Characteristics  of  Compounds  Formed. — In  a  gen- 
eral way  the  character  of  the  compounds  may  be  known 
someAvhat   from   the  position   of   the   elements  forming 
them.     Thus,  nearby  elements,  possessing  similar  char- 
acteristics would  not  be  expected  to  unite  to  form  com- 
pounds at  all.     In  the  case  of  the  metals,  most  of  the 
unions  formed  are  not  true  compounds.     With  the  non- 


272  APPLIED   CHEMISTRY 

metals,  such  as  nitrogen  and  oxygen,  nitrogen  and  chlo- 
rine, and  others,  when  such  do  form  compounds  it  is  usu- 
ally through  indirect  processes  by  which  the  two  ele- 
ments are  left  together  and  such  compounds  are  very  un- 
stable. The  oxides  of  nitrogen  already  studied,  are  all 
more  or  less  unstable;  further,  it  has  been  noted  that 
practically  all  the  explosives  are  compounds  of  nitro- 
gen and  oxygen  and  owe  their  explosive  properties  to 
the  instability  of  such  compounds.  Chlorine  and  oxygen 
form  oxides,  indirectly,  but  they  are  dangerously  explo- 
sive, as  are  also  those  of  nitrogen  and  chlorine.  On  the 
other  hand,  elements  distantly  located  in  the  table  form 
very  stable  compounds.  Thus,  sodium  and  chlorine,  or 
calcium  and  fluorine,  unite  readily  and  directly  and  form 
relatively  very  stable  compounds.  Such  are  a  few  of  the 
more  important  facts  regarding  the  periodic  table.  From 
this  time  forward  the  various  elements  studied  will  be 
taken  up  in  accordance  with  the  "Periodic  System"  or 
arrangement,  as  shown  in  the  table. 

Exercises  for  Review 

1.  What  two  divisions  of  the  elements  have  been  used  thus  far? 
Give  some  of  the  general  characteristics  of  each  division. 

2.  What   objection   is  offered  to  this  as  a  scientific  method   of 
classification? 

3.  What  is  the  basis  of  arrangement  in  Mendeleeff 's  table?   How 
did  he  come  to  discover  the  recurrence  of  properties? 

4.  What  arrangement  was  made  of  the  elements  after  the  recur- 
rence of  properties  was  observed? 

5.  What  is  a  group  in  the  table?    A  period? 

6.  State  what  is  observed  regarding  valence  in  the  table,  using 
both  the  oxygen  and  the  hydrogen  compounds.     What  is  the  valence 
of  the  argon  family?     What  is  meant  by  that  statement? 

7.  State   what   is  observed   in  passing  from   left  to   right   in   a 
period. 

8.  What  is  true  in  each  group  at  the  right  side  of  the  table  as 
the  \veight  increases? 


PERIODIC    CLASSIFICATION    OF   ELEMENTS  273 

9.  Where   does  the   dividing  line   come   in  the  table?     Give  the 
general  characteristics  of  the  elements  on  either  side  of  the  line. 

10.  What  may  be  said  of  the  elements  close  to  the  diagonal  on 
either  side?     Illustrate. 

11.  What  is  true  of  the  general  characteristics  of  the  elements 
ir.  any  particular  group?     Illustrate  by  taking  some  family  as  that 
of  sulphur  or  chlorine. 

12.  What  numerical  relation  exists  among  the  elements?     Take 
the  entire  first  period  and  show  this. 

13.  What  would  be  the  approximate  weight  of  the  unknown  ele- 
ment belonging  in  the  space  below  cesium,  in  the  sodium  family? 
At  the  right  of  radium?    At  the  right  of  molybdenum? 

14.  What  is  generally  true  of  compounds  formed  from  elements 
near  each  other  in  the  table?     Illustrate. 

15.  What   is   true    of    compounds   formed    from    distantly    placed 
elements?     Illustrate. 

16.  Why  should  arsenic  be  expected  to  have  both  basic  and  acidic 
properties?     Which  would  be  the  more  pronounced? 

17.  Would  you  expect  to  find  zinc  with  any  acidic  tendencies? 
If  so,  how  would  they  compare  with  those  of  aluminum? 

18.  Noting  the  fact  that  hydrogen  and  bromine  are  close  to  the 
diagonal,  what  would  you  expect  to  be  true  of  the  stability  of  hy- 
drogen  bromide   as   compared   with   hydrogen    chloride?      What    of 
hydrogen  iodide?     What  does  our  work  in  bromine  show? 

19.  Ought  chlorine  to  displace  bromine  from  a  compound  or  the 
reverse?     How  about  chlorine  and  iodine? 


CHAPTER  XXIII 

THE  NITROGEN  FAMILY 

Outline — 

Members  of  the  Group 
Phosphorus 

(n)   Occurrence 

(fe)   Preparation 

(c)   Forms  of 

(tZ)   Characteristics 

( e)   Uses — Poisons 
Matches 

(/)   Hydrogen   Compound 

(g)   Oxides 

(7i)   Phosphates 

(i)   Fertilizers 
Arsenic 

(a)   Occurrence 

(1)}   Characteristics 

(c)   Uses 

((7)   Arsine 

(e}   Tests  for 

(/)   Oxides  of 

(g}   Antidote  for  Poisoning 

(ft)   Pigments 
Antimony 

(a)   Characteristics 

(ft)   Uses 

(c)  Stibine 

(d)  The  Sulphide 

(e)  Tartar  Emetic 
P.ismuth 

(a)    Characteristics 
(&)   Uses 
(c)   The  Nitrates 

Tabular  Comparison  of  Compounds 
274 


THE   NITROGEN   FAMILY  275 

1.  Members   of   the   Family. — Nitrogen,   the   lightest, 
has  already  been  studied  in  connection  with  the  atmos- 
phere.    The  other  members  are  phosphorus,  arsenic,  an- 
timony  and   bismuth.     These   four   are   all   solids,   and 
the  last  three,  while  not  strikingly  alike  in  some  of  their 
physical  properties  when  untarnished,  closely  resemble 
each  other  in  their  bright  metallic  luster  and  crystal- 
line appearance ;  but  it  is  in  the  compounds  formed  and 
the  chemical  behavior  in  which  they  agree  most  closely. 

2.  Phosphorus. — Phosphorus   was   discovered  as  long 
ago  as  1669.     About  a  century  later,  1771,  Scheele  pre- 
pared it  from  bone-ash,  a  plan  which  has  been  followed 
nearly  ever  since.     The  word  phosphorus  means  liglit- 
licarer,  and  was  given  to  the  element  because  of  the  fact 
that  it  glows  in  the  dark  when  exposed  to  the  air.     In 
the  form  of  a  phosphate  rock,  calcium  phosphate,  it  oc- 
curs   abundantly   in    some    of   the    Southern    States,    es- 
pecially Florida,   South   Carolina   and   Tennessee.     It   is 
found  in  small  quantities  in  the  nerve  centers  and  muscles 
of  the  body,  but  more  largely  in  the  bones,  of  which,  as 
calcium    phosphate,    it    constitutes    about    three-fifths    in 
weight.     In  the  average  human  body  it  is  said  that  there 
are  about  3  pounds  of  phosphorus,  nine-tenths  of  which 
is  in  the  bones  and  most  of  the  remainder  in  the  muscles. 

3.  Preparation  of  Phosphorus. — Up  to  recent  years  the 
bones  of  cattle,  obtained  from  the  packing  houses,  from 
which    the    gelatine   and    oil    had    been    extracted,    were 
charred  to  form  bone  charcoal.    When  this  was  no  longer 
valuable  for  refining  sugar,  it  was  burned  to  a  white 
ash   in   the   air   and   from   this   calcium   phosphate    the 
phosphorus  was  distilled.     At  the  present  time,  native 
phosphate  rock,  supposedly  the  fossil  remains  of  birds, 
is  mainly  employed.     With  the  crushed  rock  are  mixed 
sand  and  coke  or  charcoal,  the  mixture  is  fed  into  an 


276 


APPLIED   CHEMISTRY 


electric  furnace  by  a  worm  drive  below  the  hopper,  as 
shown  in  Fig.  53.  When  strongly  heated  the  carbon  re- 
moves a  portion  of  the  oxygen,  while  the  sand  forms  a 
slag  with  the  calcium  and  is  drawn  off  at  the  bottom. 
The  phosphorus,  thus  set  free,  distils  out  in  the  form 
of  vapor,  is  condensed  under  water,  and  molded  into 
small  sticks. 

4.  Forms  of  Phosphorus. — Similar  to  several  other  ele- 
ments already  studied,  especially,  oxygen,  carbon  and 
sulphur,  phosphorus  occurs  in  two  distinct  varieties. 


Fig.    53. — Manufacture    of    phosphorus. 

Prepared,  as  described  above,  it  is  known  as  yellow 
phosphorus;  if  this  be  heated  to  a  temperature  of  250° 
C.  out  of  contact  with  the  air  red  phosphorus  is  obtained. 
5.  Physical  Characteristics. — Yellow  phosphorus,  when 
freshly  prepared  or  when  first  opened  from  a  "tin" 
container  which  has  excluded  all  light,  is  of  a  very  pale- 
amber  color,  so  nearly  colorless,  that  it  is  sometimes 
called  white  phosphorus.  It  is  of  waxy  appearance  when 
cut.  On  exposure  to  light  it  deepens  in  color,  owing  to 
the  formation  of  a  coating  of  the  red  variety.  The  yellow 
is  soluble  in  carbon  disulphide,  and  taken  internally  is 


THE    NITROGEN    FAMILY  277 

very  poisonous.  The  vapors,  continually  inhaled,  are 
also  poisonous,  and  produce  a  disease  of  the  jaw  bones, 
known  locally  as  "phossy  jaw,"  which  may  be  relieved 
only  by  surgical  operation  and  generally  is  incurable. 
The  molecular  weight  of  phosphorus  vapor  is  128,  which 
indicates  four  atoms  to  the  molecule,  formula  P4.  Red 
phosphorus  is  a  dark  reddish-brown  powder,  not  soluble 
in  carbon  disulphide.  It  is  not  poisonous  and  need  not 
be  kept  in  water  as  must  the  yellow.  If  vaporized  at 
a  temperaure  of  300  it  changes  to  the  yellow  variety ;  that 
is,  the  vapor  from  both  the  red  and  yellow  varieties  is  the 
same  and  upon  being  condensed  forms  the  unstable  va- 
riety. 

6.  Chemical  Properties. — YelloAv  phosphorus,  exposed 
to  air,  glows  in  the  dark ;  in  contact  with  chlorine  it 
catches  fire  instantly;  with  liquid   bromine,   and   after 
a  few  seconds  with  iodine,  it  does  the  same.     If  ignited, 
both  varieties  burn  in  oxygen  with  great  brilliance.     It 
is  singular,  however,  that  in  a  jar  of  oxygen,  phosphorus 
does  not  glow  at  ordinary  temperatures.     If  a  solution 
of  phosphorus  in  carbon  disulphide  be  put   upon  two 
strips  of  blotting  paper  and  inserted,  one  into  a  bottle 
of  oxygen  and  the  other  into  one  of  air,  the  latter  will 
ignite  as  soon  as  the  solvent  has  evaporated.     The  other 
remains  unaffected  unless  the  bottle  be  opened  to  the 
air  when  ignition  takes  place  only  after  from  one  to 
three  minutes  have  elapsed. 

7.  Uses. — Yellow   phosphorus    in    small    quantities    is 
used  in  poisons  for  rats,  mice  and  similar  vermin.    Most 
of    it,    however,    is    employed    in    the     manufacture     of 
matches.     The  original  sulphur  match  was  made  by  dip- 
ping pine  splints  into  molten  sulphur,  and  then  adding 
a  mixture  of  phosphorus  in  glue.     Friction  exposed  the 
phosphorus  and  ignited  it,  whereupon,  the  sulphur,  of 


278  APPLIED    CHEMISTRY 

low  kindling  point,  caught  fire  and  in  turn  the  pine 
splint.  Such  matches,  while,  vastly  better  than  none 
or  those  that  had  preceded  them,  burn  slowly  and  form 
considerable  sulphur  dioxide.  On  this  account  they  fell 
into  disfavor.  To  increase  the  speed  of  combustion 
some  oxidizing  material,  like  potassium  chlorate  or  ni- 
trate was  added;  instead  of  sulphur,  the  splints  were 
dipped  into  melted  paraffin  for  kindling.  This  gave 
a  rapid  match  and  a  serviceable  one,  but  dangerous. 
The  mixture  upon  the  head  was  too  easily  ignited;  many 
fires  were  caused  by  the  ordinary  friction  incident  to 
their  transportation.  Moreover,  owing  to  the  amount  of 
yellow  phosphorus  in  their  composition,  not  only  were 
the  workmen  in  the  factories  constantly  subjected  to  the 
fumes,  but  children  were  often  poisoned  by  them.  These 
facts  led  to  adverse  legislation  and  in  many  states 
such  matches  were  forbidden;  then  came  matches  of 
the  "Birdseye"  type,  which  contained  phosphorus  only 
in  the  tip  of  the  head  and  which  could  not  be  ignited 
by  friction  on  the  sides.  These  did  away  with  most 
of  the  fires,  but  not  with  the  poisonous  properties.  Fi- 
nally, the  United  States  government  by  levying  a  direct 
tax  of  2  cents  per  hundred  matches  legislated  them  out 
of  existence.  At  present,  ordinary  matches  are  made 
by  dipping  the  splints  into  melted  paraffin  for  kindling, 
then  into  a  mixture  of  some  compound  of  phosphorus  and 
some  oxidizing  material,  as  potassium  chlorate,  with  dex- 
trin or  glue  as  the  adhesive.  The  friction  produced  by 
"striking"  the  match  is  sufficient  to  decompose  the  phos- 
phorus compound,  ignite  the  phosphorus  and  then  the 
kindling.  The  phosphorus  compound  used  is  not  poi- 
sonous. 

8.  Safety  Matches. — In  this  variety  of  match  red  phos- 
phorus and  antimony  trisulphide  mixed  together  are  put 


THE    NITROGEN    FAMILY 


279 


upon  the  box  by  means  of  a  little  glue :  upon  the  splint 
is  the  paraffin  for  kindling,  and  antimony  trisulphide 
with  some  oxidizing  compound.  Friction  upon  the  pre- 
pared surface  of  the  box  vaporizes  a  small  portion  of  the 
red  phosphorus,  the  vapor  is  ignited  and  sets  fire  to  the 
combustible  material  upon  the  splint.  Such  matches  may 
be  ignited  upon  other  surfaces,  not  thus  prepared,  but 
a  long  stroke,  with  much  friction  is  needed  to  produce 
sufficient  heat  to  ignite  the  antimony  compound  which 
is  combustible. 


Fig.    54. — Preparation   of   phosphine. 

9.  Phosphine. — This  compound  is  a  gas  made  by  the 
reaction  of  a  solution  of  either  sodium  or  potassium  hy- 
droxide upon  yelloAv  phosphorus.  It  is  of  interest  be- 
cause of  the  fact  that  as  thus  obtained  it  ignites  spon- 
taneously on  exposure  to  the  air.  The  following  equa- 
tion shows  the  chemical  reaction, 

P4  +  3NaHO  +  3H20   -»   3NaHP02  +  PH3. 

The   reaction   takes   place   at   the   boiling   temperature, 
only  slowly  at  room  temperatures;  the  spontaneous  ig- 


280  APPLIED   CHEMISTRY 

nition  is  said  to  be  due  to  the  presence  of  a  minute  quan- 
tity of  a  liquid  hydrogen  phosphide,  P2H4.  If  the 
gas  be  collected  over  water  and  allowed  to  stand  thus 
for  several  hours,  the  liquid,  P2H4,  is  dissolved  and 
the  gas  does  not  ignite  spontaneously.  Apparatus 
such  as  was  used  for  making  hydrogen,  may  be  used, 
except  that  the  thistle  tube  should  have  substituted  for 
it  a  piece  of  ordinary  glass  tubing  bent  at  the  upper 
end  as  shown  in  Fig.  54.  This  must  reach  to  the  bot- 
tom of  the  flask.  Before  applying  heat  the  air  must 
be  removed;  this  is  most  easily  done  by  attaching  the 
gas  supply  to  the  bent  tube  and  running  the  gas  through 
for  two  or  three  minutes.  The  same  should  be  repeated 
at  the  close  of  the  experiment,  otherwise  as  the  air  en- 
ters to  take  the  place  left  by  the  contracting  gas  as  it 
cools,  it  will  cause  an  explosion.  As  the  bubbles  of  phos- 
phine  come  to  the  surface  of  the  water  in  the  trough 
they  ignite  spontaneously  and  in  still  air  rings  of  white 
"smoke"  float  upward.  The  gas  has  no  practical  uses. 
10.  The  Oxides. — Phosphorus  forms  two  common  ox- 
ides, the  trioxide  and  pentoxide,  P203,  and  P205,  both 
produced  by  burning  of  phosphorus  in  the  air.  When 
the  supply  is  plentiful,  the  higher  oxide  is  obtained; 
when  limited,  the  trioxide.  They  are  both  white  solids 
and  are  the  anhydrides  of  acids.  Thus, 

P203  +  3H20-»2H8P08, 

P205  +  H20  -»  2HP03. 

The  latter  is  very  vigorous  in  chemical  action  such  that 
when  the  oxide  is  dropped  into  water  a  hissing  sound 
like  that  of  a  hot  iron  touching  the  water  is  heard.  The 
acid  produced  is  known  as  meta-  or  glacial  phosphoric 
.acid  and  corresponds  to  nitric  acid,  HN03.  If  the  pen- 


THE    NITROGEN   FAMILY  281 

toxide  is  put  into  boiling1  hot  water  the  reaction  is  dif- 
ferent, thus, 

3H20  +  PA  ->  2H3P04. 

This  is  known  as  orthophosphoric  acid.  Upon  heating, 
it  loses  water  and  changes  into  the  metaphosphoric. 

11.  Phosphates. — Salts    of    orthophosphoric    acid    are 
called  phosphates.     The  most  common  are  those  of  so- 
dium, potassium  and  calcium.     These  are  found  in  most 
soils  in  sufficient  quantities  for  plant  growth,  but  suc- 
cessive cropping,  especially  by  various  grains  such  as 
wheat  or  corn,  remove  them  to  such  an  extent  that  they 
must  be  replaced  by  fertilizers.     The  human  body  re- 
quires phosphates  for  the  bones,  muscles  and  nerve  cen- 
ters.    This  is  obtained  mainly  through  the  cereal  foods, 
although  eggs,  beans  and  peas  also  contain  it. 

12.  Fertilizers. — The    three    things    most    needed    for 
plants  to  insure  vigorous  growth  and  production  of  fruit 
or  seed  are  nitrogen,  phosphorus  and  potash.     Means 
of  procuring  the  nitrogen  have   already  been  studied. 
Two  important  sources  of  phosphates  are  the  native  rock 
already  mentioned  and  bone  products  from  the  packing 
houses.    Neither  of  these  compounds  is  soluble  in  water 
and   hence    unavailable    for    plant   food.      However,    if 
treated  with  sulphuric  acid,  they  are  converted  into  an 
acid  phosphate,  CaII4(P04),,  which  is  soluble  in  water 
and  therefore  suitable  as  a  fertilizer.     The  reaction  is 
shown  thus, 

Ca3(P04),  +  2H2S04  -»  2CaS04  +  CaH4(P04)2 

Phosphorus-bearing  iron  ores  are  also  a  source  of  a  con- 
siderable amount  of  the  same  acid  phosphate,  commercially 
known  as  the  "superphosphate."  It  is  said  that  in  soils 
containing  much  humus  the  acids  formed  by  the  decom- 
position of  the  organic  matter  slowly  convert  native 


282  APPLIED    CHEMISTRY 

phosphate   into   the   superphosphate   and   thus   make   it 
available. 

13.  Arsenic. — This  element,  third  in  density  in  the  ni- 
trogen family,  occurs  in  nature  in  arsenical  iron  pyrite 
(FeAs)S;  also  as  realgar  and  orpiment,  both  sulphides 
of  arsenic.     The .  first  named  is  the  usual  source  of  the 
commercial  supply. 

14.  Characteristics. — Arsenic  as  obtained  from  the  py- 
rite is  of  a  dark  gray  color,  and  as  usually  seen,  not 
lustrous.     Upon  heating  in  an  open  dish  the  dull  coat- 
ing disappears,   leaving  the  element   in  its  natural   lus- 
trous, steel-gray  color.    It  vaporizes  upon  heating  without 
melting,   at  a  temperature  of  180°   C.     The  molecular 
weight  of  the  vapor  is  300  which  is  four  times  the  atomic 
weight.     This  shows  that  the  formula  for  the  molecule, 
like  that  of  phosphorus,  is  As4.     Powdered  arsenic  sifted 
into  a  jar  of  chlorine  ignites  spontaneously  and  burns  as 
it  falls;  on  bromine,  it  combines  likewise  with  vigor.     In 
the  air  it  burns  with  a  purplish  white  light  and  forms 
heavy  white  fumes  of  the  trioxide,  As203. 

15.  Uses. — There  are  few  uses  for  the   element.     In 
the  manufacture  of  shot  from  lead  about  1  per  cent  of 
arsenic  is  added.     The  main  reason  for  this  is  that  the 
mixture  of  lead  and  arsenic  is  when  molten  much  more 
limpid  or  mobile  than  pure  lead.     As  a  result,  in  pour- 
ing, the  liquid  is  broken  up  the  more  easily  and  the  shot 
are  much  more  perfect.     They  are  at  the  same  time  a 
shade   harder  than  they  would  be   otherwise.     As  the 
melting  point  of  the  mixture  is  lower  than  that  of  lead 
alone,  solidification  does  not  take  place  so  rapidly,  which 
gives  the  shot  more  time  in  assuming  perfect  spherical 
form. 

16.  Arsine. — As  nitrogen  and  phosphorus  form  hydro- 
gen compounds  so  does  arsenic,  with  a  formula  corre- 


THE    NITROGEN    FAMILY  283 

spending  to  that  of  ammonia  and  phosphine.  It  is  visu- 
ally prepared  by  adding1  to  a  hydrogen  generator  a  so- 
lution of  arsenic.  It  is  usually  not  collected,  but  burned 
as  generated.  The  equations  show  the  chemical  reac- 
tions taking  place, 

Zn  +  ILS04  ->  ZnS04  +  2II, 
AsCl3  +  611  ->  AsH3 


In  the  equation  it  may  be  noticed  that  the  hydrogen  was 
not  written  IL,  as  has  been  done  in  previous  cases,  when 
it  has  been  collected  in  the  molecular  condition.  In 


Fig.    55. — Marsh's   test    for    arsenic. 

the  present  instance  it  reacts  with  the  arsenic  as  fast 
as  it  is  set  free  from  the  acid  and  is  said  to  be  in  the 
nascent  condition.  The  term  means  being  set  free.  In 
such  condition  it  is  much  more  active  than  in  the  molec- 
ular form.  Some  chemists  offer  a  different  explanation 
for  the  greater  activity  but  the  term  is  commonly  used  and 
should  be  understood.  The  arsine  obtained  thus  always 
contains  an  admixture  of  hydrogen,  but  this  does  not  in- 
terfere with  the  study  of  it. 

17.  Characteristics. — Arsine  is  a  colorless  gas  with  a 
somewhat   offensive   and   nauseating   odor.     It   may  be 


284  APPLIED   CHEMISTRY 

liquefied  at  -40°  C.  It  is  exceedingly  poisonous,  so  that 
small  quantities  inhaled  may  result  fatally.  It  is  easily 
decomposed  by  heat  as  shown  by  the  equation, 

4AsH3  -H>  As4  +  6H2. 

This  is  easily  shown  experimentally.  If  a  hard  glass 
tube  is  attached  to  the  arsine  generator  and  a  Bunsen 
flame  is  placed  beneath  the  tube,  the  arsine  is  decom- 
posed; and  at  a  short  distance  beyond  the  heated  portion 
a  black  ring  of  the  arsenic  appears,  while  the  hydrogen 
escapes  from  the  tube  and  may  be  burned.  The  plan  is 
simplified  oftentimes,  as  shown  in  Fig.  55,  by  holding 
a  cold  dish  against  a  small  arsine  flame.  Brownish 
black  spots  with  metallic  luster  appear  upon  the  dish. 
The  explanation  is  the  same  as  before;  the  vapor  of  ar- 
senic obtained  by  the  dissociation  of  the  arsine  is  con- 
densed in  solid  form  upon  the  cold  dish.  This  is  usually 
spoken  of  as  Marsh's  test  for  arsenic,  and  is  exceedingly 
delicate.  The  merest  traces  may  be  detected  in  this 
manner.  The  reaction  when  the  arsine  is  burning  freely 
in  the  air  is, 

2AsH3  +  302  -»  3H20  +  As203. 

The  white  fumes  appearing  are  the  trioxide  of  arsenic. 
When  a  cold  dish  is  held  in  the  flame,  this  equation 
shows  what  is  happening, 

4AsH3  +  302  -»  6H20  +  As4. 

The  hydrogen  continues  to  burn,  but  the  arsenic  vapors 
are  condensed  in  solid  form.  In  making  this  test  precau- 
tion must  be  taken  not  to  light  the  escaping  gas  until  all 
the  air  is  removed  from  the  flask.  A  serious  explosion  is 
apt  to  result  if  this  is  not  done. 

18.  The  Oxides. — There  are  two  oxides  of  arsenic,  the 
trioxide,  As203,  and  the  pentoxide,  As205.     The  first  is 


THE   NITROGEN   FAMILY  285 

much  the  more  common.  In  commerce  it  is  sold  under 
three  other  names :  arsenious  acid,  a  misnomer,  for  it  is 
merely  the  anhydride  of  arsenious  acid,  "white  arsenic," 
and  "arsenic." 

19.  Characteristics  of  the  Trioxide. — Usually  it  is  ob- 
tained as  a  white  powder,  although  occasionally  as  a 
colorless,  glass-like  solid.     Like  iodine,  carbon  dioxide 
snow,  and  elementary  arsenic  it  vaporizes  without  melt- 
ing.   It  is  slightly  soluble  in  water  and  forms  the  corre- 
sponding acid,  thus, 

As203  +  3H20  ->  2H3As03. 

Taken  internally  it  is  a  poison,  but  because  of  the  fact 
that  it  is  not  very  soluble  it  acts  slowly.  It  is  used 
very  commonly  as  a  poison  for  vermin  and  in  large 
quantities  in  spraying  apple  trees  to  destroy  coddling 
moth.  For  this  purpose  it  is  usually  combined  with  lead 
acetate  to  form  lead  arsenite.  This  compound  is  the 
most  desirable  because  on  account  of  insolubility  it  is 
not  washed  away  readily  by  rains  and  for  the  same  rea- 
son does  not  "burn"  the  foliage.  Arsenic  trioxide  is 
used  to  some  extent  in  preserving  skins  in  taxidermy 
and  to  a  limited  degree  in  medicine,  especially  Fowler's 
solution,  a  solution  of  the  trioxide  in  potassium  hy- 
droxide. 

20.  Antidotes   for   Arsenic   Poisoning. — The   antidote 
most   generally  recommended   for   arsenic   poisoning   is 
freshly  prepared  ferric  hydroxide.     It  is  quickly  made 
by  putting  together  ferric  chloride  solution  and  ammo- 
nia water,  taking  care  that  the  ammonia  be  not  present 
in  great  excess.     A  heavy,   brownish,   flocculent  precip- 
itate   of    ferric    hydroxide    is    formed    and    this,    filtered 
out,  is  used  in  a  glass  of  water.     The  ferric  hydroxide 
combines   with    the    arsenic    forming    an    insoluble    com- 


286  APPLIED  CHEMISTRY 

pound  which  as  a  result  cannot  be  absorbed  by  the  sys- 
tem. An  emetic  or  stomach  pump  should  follow  the 
antidote.  Another  sometimes  used,  which  is  easier  to 
obtain  but  slower  in  action,  is  magnesium  oxide,  com- 
monly sold  as  magnesia.  Its  chemical  action  is  the 
same  as  the  ferric  hydroxide. 

21.  Paris  Green. — This  is  rather  a  complicated  com- 
pound    as     shown     by     the     formula,     Cu(C2H302)2  + 
CuHAsOg.    It  will  be  seen  that  it  consists  of  copper  ace- 
tate   and    acid    copper    arsenite,    combined.      Scheele's 
green   is   acid   copper   arsenite,   CuHAs03.     Both   com- 
pounds are  bright  green  pigments  and  formerly  were 
used  extensively  in  coloring  wall  papers.     Through  the 
probable  action  of  the  decomposing  paste  upon  the  ar- 
senic   compound,    volatile    compounds    were    produced 
which  are  very  poisonous  and  serious  results  often  fol- 
lowed.   Coal  tar  dyes  have  now  entirely  supplanted  these 
pigments  for  wall  papers.     Paris  green  is  abundantly 
used  in  spraying  or  dusting  potato  plants  to  kill  the  Col- 
orado beetle.    For  small  patches  the  powder  mixed  with 
flour  or  air-slaked  lime  is  dusted  upon  the  plants  when 
wet  with  dew  by  means  of  a  " shaker,"  homemade  from 
a  baking  powder  or  similar  can,  by  perforating  the  top 
with  numerous  holes.     On  a  large  scale  the  Paris  green 
is  usually  mixed  in  water  and  sprayed  on  by  pumps. 

22.  Characteristics    of    Antimony. — In    the    nitrogen 
family   antimony   follows    arsenic    in   density   with   an 
atomic  weight  of  120.2.    It  is  a  highly-crystallized,  lust- 
rous, steel-white  metal.     Like  arsenic  it  is  very  brittle, 
but  does  not  tarnish  as  readily  in  the  air.     It  has  a 
melting  point  of  about  445  and  upon  solidifying  it  ex- 
pands greatly.     It  combines  readily  with  chlorine  and 
bromine,  and  heated  in  the  air,  burns  to  antimony  triox- 
ide. 


THE    NITROGEN    FAMILY  287 

23.  Uses  of. — In  the  form  of  antimony  black,  a  very 
finely  powdered  or  precipitated  antimony,  it  is  often  used 
upon  plaster  casts  to  give  them  a  metallic  appearance.    Its 
chief  use  is  in  alloys.     By  an  alloy  is  meant  an  intimate 
mixture  of  two  or  more  metals,  melted  together.     They 
are   generally   really   solutions,    although   some    few    are 
known  which  seem  to  partake  somewhat  of  the  nature  of 
a   compound.     The  more   important   alloys  of   antimony 
are  brittania,.  pewter,  babbitt,  stereotype  and  type  metal. 
The  first  two  are  alloys  of  copper,  tin  and  antimony  and 
are  used  mainly  because  they  do  not  tarnish  greatly  in 
the  air.     Babbitt  is  used  for  bearings  in  machinery,  as 
for  example  those  of  the  crank  shaft  in  motor  cars,  to 
reduce  friction.    Type  metal  consists  of  antimony,  tin  and 
lead   and   is   of  the   utmost   importance.      The   antimony 
causes  the  expansion  of  the  type  metal  when  it  solidifies 
and  thus  gives   sharp   outlines  to  all   the  finest   details. 
Made  of  lead  alone,  which  contracts  upon  cooling,  type 
would  give  prints  entirely  illegible.    The  purpose  of  anti- 
mony in  stereotypes  is  the  same. 

24.  Stibine. — Antimony  forms  the  hydride,  SbII3,  cor- 
responding to  those  of  the  members  of  this  family  al- 
ready studied.     It  may  be  prepared  as  was  arsine.     It 
may  be  liquefied  at  -18°  C.     It  is  even  more  easily  dis- 
sociated by  heat  than  is  arsine  and  gives  the  same  spots 
upon  a  porcelain  dish  as  does  the  arsenic,  although  they 
are  black  rather  than  brown,  more  soft  and  velvety  in 
appearance.     If  heat  be  applied,  since  arsenic  is  vola- 
tile, spots  made  by  arsine  will  disappear,  while  the  anti- 
mony will  not.    Further,  a  solution  of  bleaching  powder 
will  dissolve  the  arsenic  spots  and  leave  the  antimony 
unaffected. 

25.  Antimony    Trichloride,     SbCl3. — This    compound 
may  be   made  by  dissolving   antimony   in   aqua   regia. 


288  APPLIED    CHEMISTRY 

It  is  sometimes  called  butter  of  antimony,  because  of 
the  fact  if  not  concentrated  to  the  point  of  crystallization, 
it  is  an  oily,  yellow  liquid,  resembling  melted  butter.  In 
the  solid  form  it  is  white  and  crystalline.  If  water  is 
added,  partial  solution  takes  place  with  the  precipitation 
of  a  white  compound  having  the  formula,  SbOCl,  anti- 
mony oxychloride.  The  reaction  is 

SbCls  +  H20  ?±  SbOCl +  2HC1. 

By  cautiously  adding  hydrochloric  acid  and  stirring,  the 
reaction  is  entirely  reversed ;  upon  adding  more  water  the 
white  precipitate  again  appears.  It  is  an  interesting  case 
because  it  is  one  of  the  few  in  which  reversibility  is  easily 
seen. 

26.  Antimony  Trisulphide,   Sb,S3. — Found   in   nature 
this   compound  is   steel-gray,   about  the   color   of  lead. 
Prepared  in  the  laboratory  by  passing  a  current  of  hy- 
drogen sulphide  through  a  solution  of  some  antimony 
compound,  it  is  a  beautiful  orange  colored  precipitate 
which  turns  dark  if  melted.     It  is  used  extensively  in 
the  preparation  of  matches  as  previously  stated. 

27.  Tartar  Emetic,  KSbOC4H406. — From  the  formula 
this  compound  is  seen  to  be  basic  antimony  potassium 
tartrate.     It  is  one  of  the  few  basic  salts  we  have  seen. 
It  is  a  white  solid  and  unlike  the  chloride  is  completely 
soluble  in  water.    It  is  used  somewhat  in  medicine  as  an 
emetic,  but  like  all  antimony  compounds  is  very  poison- 
ous. 

28.  Characteristics   of   Bismuth. — Bismuth   resembles 
antimony  in  general  appearance  in  that  it  is  highly  crys- 
talline in  structure,  but  its  color  is  darker  and  of  a  pur- 
plish or  golden  luster.     It  is  very  brittle,  much  heavier 
than  antimony  with  an  atomic  weight  of  208.     It  melts 
at  about  270°  C.   With  chlorine  and  bromine  its  behavior 


THE    NITROGEN    FAMILY  289 

is  about  the  same  as  that  of  antimony.     Upon  solidify- 
ing the  metal  expands  greatly. 

29.  Uses. — While  it  is  eminently  suited  for  type  metal 
on  account  of  its  expansibility,  being  much  more  ex- 
pensive, it  is  rarely  thus  used,  except  in  delicate  stereo- 
types. One  of  its  most  important  uses  is  in  making 
alloys  of  low  fusing  point.  Some  of  them  are  very  re- 
markable in  this  respect.  Thus  : 


ALLOY 

BISMUTH 

LEAD 

TIN 

CADMIUM 

MELT.   PT. 

Wood's  Metal 
Rose  's  Metal 

4  parts  (270°) 
82  parts 

2    (825°) 
9  parts 

1    (232°) 
9  parts 

1    (820°) 
none 

60.5°C. 

94°C. 

It  will  be  seen  that  both  these  alloys  melt  below  the 
temperature  of  boiling  water,  one  of  them  much  below. 
Thus,  spoons  cast  of  the  former,  if  placed  in  a  cup  of  hot 
tea  or  coffee  would  be  melted  and  drop  to  the  bottom. 
They  are  interesting  illustrations  of  the  fact  brought 
out  that  solutions  have  their  freezing  point  lowered. 
In  these  alloys  bismuth  may  be  regarded  as  the  solvent 
with  a  freezing  point  of  270°  C.  for  freezing  point  and 
melting  point  are  the  same.  When  the  other  metals  are 
dissolved  in  this,  the  freezing  point  is  lowered,  in  one 
case  to  94°  and"  in  the  other  to  about  60°  C.  This  low 
melting  property  of  bismuth  alloys  enables  it  to  be  em- 
ployed in  a  variety  of  interesting  ways.  Most  city  or- 
dinances require  that  the  lanterns  for  moving  picture 
shows  be  enclosed  in  a  metal  or  fire-proof  booth.  The 
openings  are  provided  with  shutters  held  open  by  a 
chain  one  link  of  which  is  made  of  an  easily  fusible  al- 
loy. In  case  of  the  film  taking  fire  this  link  is  easily 
melted,  the  shutter  closes  automatically  and  the  fire  is 
kept  within  the  booth.  Metal  fire  doors,  between  dif- 
ferent apartments  in  large  manufacturing  establish- 
ments, are  often  held  open  during  the  day  by  fusible 


290  APPLIED    CHEMISTRY 

metal  devices.  In  case  of  fire,  the  metal  melts  and  the 
door  is  closed  by  the  ordinary  air  spring  attached.  Au- 
tomatic sprinkling  systems  in  large  department  and 
wholesale  houses  employ  the  same  principle.  Plugs  in 
the  pipes  occur  at  intervals;  if  fire  occurs  they  are 
melted  and  the  water  is  turned  on  automatically.  Steam 
boilers  are  likewise  often  provided  with  fusible  plugs, 
such  as  to  melt  out  and  allow  the  escape  of  the  steam 
before  the  danger  point  is  reached. 

30.  Compounds. — Not  many  of  these  are  of  sufficient 
importance     to     need     attention     here.       The     nitrate, 
Bi(N03)3,  is  a  white  crystalline  solid,  prepared  by  treat- 
ing  bismuth   with   nitric    acid.      The   reaction   is    thus 
shown, 

Bi  +  4HN03  -»  Bi(NOs)3  +  2H20  +  NO. 

When  water  is  added  a  white  precipitate  forms  of  the 
basic  or  oxynitrate, 

Bi(NOs)3  +  H20  *=±  BiON03  +  2HN03. 

Tested  with  litmus  paper  the  solution  is  found  to  be 
acidic  as  is  true  also  when  antimony  chloride  is  dis- 
solved in  water.  The  reaction  is  also  equally  reversible, 
as  may  be  shown  by  the  cautious  addition  of  nitric  acid. 
This  white  precipitate  is  sold  under  the  name  "subni- 
trate"  of  bismuth  and  is  used  frequently  in  medicine, 
as  a  cosmetic  and  for  stomach  trouble.  Bismuth  forms 
no  compound  corresponding  to  those  of  arsine  and  stib- 
ine. 

31.  Comparison  of  the  Members  of  the  Family. — Ni- 
trogen and  phosphorus  in  their  outward  appearance  at 
ordinary   temperatures    differ    greatly   from   the    other 
three.     Nevertheless,   nitrogen  at  low  temperatures   is 
a  white  solid  and  phosphorus  nearly  so.     In  their  chem- 
ical behavior  they  are  very  similar  in  most  respects.    As 


THE    NITROGEN    FAMILY 


291 


stated  elsewhere,  as  the  elements  in  a  group  increase  in 
weight,  the  tendency,  seen  best  in  the  oxides,  is  to  be- 
come basic  or  metallic  in  character.  Thus  the  oxides 
of  nitrogen  and  phosphorus  are  strongly  acidic;  of  ar- 
senic, the  trioxide  has  a  double  character,  being  both 
basic  and  acidic.  It  reacts  with  hydrochloric  acid 
to  form  arsenious  chloride,  and  with  sodium  hydrox- 
ide to  form  sodium  arsenite.  The  pentoxide,  As205,  is 
acidic  as  might  be  expected  with  its  higher  percentage 
of  oxygen.  In  the  case  of  antimony,  the  trioxide  is  also 
of  dual  character,  but  more  strongly  basic  than  acidic, 
while  the  pentoxide  is  still  acidic.  With  bismuth  the 
trioxide  is  basic  only.  As  further  showing  this  same 
fact,  nitrogen  and  phosphorus  form  no  salts  with  these 
as  the  positive  ions ;  arsenic  forms  but  few,  not  very  sta- 
ble, antimony  and  bismuth  many,  especially  the  bismuth. 
The  following  table  compares  the  several  members  in 
regard  to  other  compounds  not  already  named: 

TABLE  FOR  COMPARISON 


NITROGEN 

N  =  14 

PHOSPHOR- 
US 

P  =  31 

ARSENIC 

As  =  75 

ANTIMONY 

Sb  =  120 

BISMUTH 

Bi  —  208 

Hydrogen 
Compound 

Ammonia 
NH3 

Phosphine 
PH3 

Arsine 

AslL 

Stibine 
SbH3 

None 

Oxides 

N.,(X 

NA 

PA 

PA 

AsA 

AsA 

SbA 
SbA 

BiA 
BiA 

Chlorides 

NC13 

PC13 

AsCl3(?) 

SbCl3 

BiCl3 

Oxychlorides 

NOC1 

POCl 

SbOCl 

BiOCl 

Acids 

HN03 

HPOg 

H3P04 

H3AsO4 

H3Sb04 

.None 

»  i 

Exercises  for  Review 

1.  Name  the  members  of  the  nitrogen  group. 

2.  From  what  has  phosphorus  been  mostly  prepared?     What  in 
very  late  years?     Give  a  brief  outline  of  the  process. 


292  APPLIED    CHEMISTRY 

3.  Name  the  forms  of  phosphorus.     Compare  them  with  sulphur. 
What  other  elements  studied  have  been  seen  in  allotropic  forms? 

4.  Give   the   characteristics   of   yellow   phosphorus   and   compare 
with  it  the  red. 

5.  Which  is  the  poisonous  variety?     What  disease  do  the  vapors 
produce?    What  remedy  is  there  for  it? 

6.  What  is  the  chief  use  of  phosphorus?     Give  another  use. 

7.  Give  the  various  steps  in  the  evolution  of  the  common  match 
as  we  have  it  to-day. 

8.  Describe  the  safety  match  and  state  how  different  from  the 
ordinary. 

9.  How  is  phosphine  made  ?     What  is  the  chief  point  of  interest 
regarding  it?     What  use  has  it? 

10.  Name  the   oxides   of  phosphorus   and   give   formulas.     How 
prepared? 

11.  Name  two  or  three  acids  of  phosphorus  and  state  how  they 
may  be  obtained  from  the  oxides. 

12.  What  phosphates  occur  in  nature?     Of  what  use  are  they? 
How  are  they  produced  artificially  for  fertilizers? 

13.  Give  the  chief  characteristics  of  arsenic. 

14.  Explain  the  purpose  of  the  one  use  of  arsenic. 

15.  How  is  arsinc  made?     How  can  you  show  that  it  is  readily 
decomposed  by  heat? 

16.  What  is  a  nascent  gas?     How  different  from  the  molecular 
form  ? 

17.  Describe  Marsh's  test  in  full. 

18.  Name  the  oxides  of  arsenic  and  give  formulas. 

19.  Describe  the  trioxide  and  give  uses.     What  is  the  antidote 
for  arsenic  poisoning?     Why  may  so  much  time  be  taken  in  pre- 
paring the  antidote? 

20.  AVhat  two  pigments  of  arsenic  are  common1?     What  former 
use  had  they?     Why  no  longer  used  this  way?     Chief  use  now? 

21.  Give  characteristics  of  antimony  and  compare  with  arsenic. 

22.  What  is  antimony  black?     Use  of  it? 

23.  Name  the  most  important  alloys  of  antimony  and  give  some 
use  of  each?     What  is  an  alloy? 

24.  Give  composition  of  type  metal  and  state  wherein  is  its  chief 
value. 

25.  How  is   stibine  made?     How  can  its   spot  be  distinguished 
from  that  made  by  arsine? 


THE   NITROGEN    FAMILY  293 

26.  What  is  butter  of  antimony?     How  made?     Why  so  called? 
When  water  is  added  to  it,  what  results?     Write  the  equation. 

27.  What  do  you  call  an  equation  like  the  above?     How  can  you 
prove  that  it  is  reversible? 

28.  How  is  antimony  trisulphide  formed  in  laboratory?     Of  what 
practical  use  is  it? 

29.  Give  use  of  tartar  emetic. 

30.  Describe  bismuth  and  compare  with  antimony. 

31.  Give  chief  uses  of  bismuth. 

32.  Name  two  very  fusible  alloys  of  bismuth.     Why  do  they  have 
such  a  low  melting  point? 

33.  Name  two   compounds   of  bismuth  and  state  how   prepared. 

34.  Write  the  equation  showing  the  reaction  of  water  with  the 
nitrate. 

35.  What  kind  of  an  equation  is  this?     How  can  you  show  ex- 
perimentally that  it  is  reversible? 

36.  Give  a  general  comparison  of  the  members  of  the  group. 

37.  Show  how  they  become  less  acidic  as  they  increase  in  weight. 

38.  Compare    the    various    oxides    of    the     group    in    chemical 
behavior. 


CHAPTER  XXIV 

COMPOUNDS  OF  SILICON 
Outline- 
Natural  Compounds — Silica 
(a)   Variety  of 
(6)   Characteristics 
(c)   Uses 
Artificial  Compounds 

(a)   Water  Glass 
(&)   Crown  Glass 

(c)  Bohemian  Glass 

(d)  Flint  Glass 
Manufacture  of  Glass  Articles 
Annealing  Glass 

1.  Occurrence  of  Silicon. — Silicon  belongs  to  the  car- 
bon group.  The  latter  element  has  already  been  stud- 
ied. Two  metals,  tin  and  lead,  also  belong  to  this  group. 
They  all  have  a  valence  of  four.  Next  to  oxygen,  silicon 
is  the  most  abundant  of  all  the  elements  and  constitutes 
something  more  than  25  per  cent  of  the  earth's  crust. 
It  is  never  found  free  as  is  carbon.  In  the  combined 
form,  sand,  Si02,  is  a  very  abundant  mineral.  Sandstone 
is  the  same  with  some  cementing  material  holding  the 
particles  together.  Crystallized,  this  same  compound 
often  occurs  as  hexagonal  prisms;  when  transparent  it 
is  then  called  rock  crystal.  When  delicately  colored 
it  is  known  as  rose  quartz,  amethyst,  milky,  and  smoky 
quartz,  according  to  the  nature  of  the  coloring.  Opals, 
agate,  chalcedony,  jasper,  flint  and  onyx  are  other  well- 
known  varieties.  Much  of  the  agate  is  petrified  wood; 
as  the  cells  of  the  woody  structure  have  been  broken 
down  in  the  process  of  very  slow  decomposition  the  sil- 

294 


COMPOUNDS    OF    SILICON  295 

ica  has  replaced  them.  The  different  colors  are  due  to 
different  compounds  dissolved  in  the  silica  when  it  was 
deposited.  The  most  noted  of  these  petrified  forests  is 
near  Adamana  in  Arizona.  Here  trunks  of  trees  of  all 
sizes,  for  the  most  part  broken  squarely  across,  are 
found  in  great  numbers,  covering  many  square  miles 
in  area.  Many  of  the  rocks  constituting  the  crust  of 
the  earth  are  compounds  of  silicon.  Such  are  kaolin, 


Fig.  56. — A  scene  in  one  of  the  petrified  forests  in  Arizona. 

feldspar,  and  the  clays  resulting  from  the  decomposition 
of  the  latter.  Mica,  which  has  the  property  of  splitting 
into  thin  sheets,  commonly  used  in  stoves  and  often  re- 
ferred to  erroneously  as  isinglass,  is  a  silicate.  Granite 
is  ordinarily  a  mixture  of  quartz,  feldspar  and  mica. 
Pumice  stone  is  a  porous  lava,  used  as  an  abrasive  and 
in  some  washing  powders,  as  "Dutch  Cleanser."  In- 
fusorial earth,  spoken  of  in  connection  with  the  manu- 
facture of  dynamite,  is  a  porous,  siliceous  rock  formed 


296  APPLIED    CHEMISTRY 

from  the  shells  of  microscopic  animals.    Fig.  56  is  a  view 
of  a  portion  of  the  petrified  forests  of  Arizona. 

2.  Characteristics  of  Silica. — If  pure,  silica  is  color- 
less.   It  ranks  seventh  in  the  scale  of  hardness,  in  which 
the  diamond  is  tenth.     It  is  not  soluble  in  any  acid  ex- 
cept hydrofluoric,  but  is  somewhat  readily  so  in  alkalies. 
Some  of  the  hot  springs  in  Yellowstone  Park  contain 
very  considerable  quantities  of  dissolved  silica,  so  that 
articles  left  where  the  spray  may  fall  upon  them,  or  if 
dipped  into  the  water  repeatedly  become  covered  with 
a  silicious  coating.     Its  melting  point  is  so  high  that- 
only  the  electric  arc  or  the  oxyhydrogen  lamp  is  suffi- 
cient to  fuse  it. 

3.  Uses  of  Some  Forms  of  Silica. — The  uses  of  sand 
for  "building  purposes  in  mortar  and  cement  are  well 
known.    For  such  work  a  coarse  sand,  with  grains  more 
or   less   rough,   and  not   well   polished,   makes   a   much 
stronger  wall  or  foundation.     All  glass  requires  sand 
for  its  manufacture ;  sand  papers  of  all  degrees  of  fine- 
ness are  made  for  polishing  and  smoothing  wood  sur- 
faces.    Pure  sand  is  now  being  made  into  crucibles  and 
various  other  chemical  apparatus,  preferable  in  many 
ways  to  glass.    As  its  coefficient  of  expansion  is  very  low, 
it  is  much  less  liable   to   be   broken   by   sudden   great 
changes  in  temperature.     The  finer   grained  infusorial 
earths  are  used  as  abrasives  for  polishing  metals,  while 
sandstone  is  made  into  whetstones  and  grindstones  for 
sharpening  tools.     The  tinted  varieties  of  quartz  men- 
tioned are  often  cut  and  mounted  in  cheaper  jewelry, 
where,  owing  to  their  hardness,  they  are  very  service- 
able.   Lenses  for  optical  instruments  and  spectacles  are 
sometimes  made  from  pure  quartz. 

4.  Silicic   Acid. — Silicon   dioxide,    Si02,   is   an   acidic 
oxide  as  would  be  indicated  by  the  fact  that  it  combines 


COMPOUNDS    OF   SILICON  297 

so  readily  with  alkalies.  Theoretically,  it  is  the  anhy- 
dride of  silicic  acid,  but  as  it  is  neither  soluble  in  water 
nor  reacts  with  it,  silicic  acid  is  not  obtainable  by  di- 
rect means.  Orthosilicic  acid  has  the  formula  H4Si04, 
but  when  precipitated  from  a  silicate  it  loses  a  molecule 
of  water  and  becomes  H,Si03.  Many  salts  of  these  two 
acids  are  known. 

5.  Water  Glass.— When  silica  is  fused  with  sodium 
carbonate,  the  following  reaction  takes  place, 

Si(X  +  Na2C03  ->  Na2Si03  +  C02. 

This  sodium  salt  of  silicic  acid  is  generally  used  in  the 
liquid  form,  or  solution,  somewhat  resembling  glycerine 
in  appearance.  If  all  water  is  removed,  a  transparent, 
colorless  solid  remains,  closely  resembling  glass.  In  the 
viscous  solution  it  is  often  called  "water  glass."  At  the 
present  time  very  large  quantities  of  it  are  used.  It  is 
probably  the  best  preservative  of  eggs.  For  this  pur- 
pose, a  mixture  of  one  part  water  glass  and  nine  parts 
of  water  are  put  into  a  jar  of  suitable  size.  Into  this  are 
put  the  eggs  from  day  to  day,  the  fresher  the  better.  It 
is  well  not  to  make  up  a  very  great  quantity  of  the 
solution  at  one  time,  although  there  should  be  sufficient 
to  keep  the  eggs  covered.  Any  egg  which  floats  in  the 
solution  should  be  discarded  as  it  is  already  stale  and 
may  be  the  cause  of  spoiling  others.  Eggs  decompose 
because  of  bacteria,  which  pass  through  the  shell  along 
with  the  air  as  it  takes  the  place  of  the  moisture  which 
is  being  constantly  evaporated.  The  water  glass  fills  and 
closes  the  pores  of  the  shell  and  thus  prevents  this  inter- 
change. Eggs  may  be  thus  kept  for  months  and  are 
always  far  preferable  to  storage  eggs  even  of  less  age.  The 
jar  and  contents  must  be  stored  where  the  contents 
will  not  freeze,  although  a  warm  room  is  not  desirable. 


298  APPLIED    CHEMISTRY 

It  may  be  remembered  that  the  solution  will  have  a 
freezing  point  much  lower  than  that  of  water;  hence  it 
will  stand  a  considerable  degree  of  cold.  It  is  well  to 
know  that  such  eggs  cannot  be  boiled  without  the  shells 
cracking,  as  a  rule.  This  is  because  at  the  boiling  point 
the  air  contained  would  be  greatly  expanded ;  because  it 
cannot  pass  through  the  pores  of  the  shells,  it  bursts 
them.  After  standing  for  some  months  a  white  gelati- 
nous mass  will  be  found  collecting  in  the  bottom  of  the 
jar.  This  is  silicic  acid,  and  is  formed  as  indicated  by 
the  equation, 

Na2Si03  +  2H20  ->  H2Si03  +  2NaHO. 

It  has  been  said  that  water  does  not  ionize  and  for  that 
reason  is  not  a  conductor  of  electricity.  It  does,  how- 
ever, ionize  to  a  very  slight  extent,  so  that  there  are  al- 
ways a  few  hydrogen  and  a  few  hydroxyl  ions  present  in 
the  water.  Thus, 

H20  *±  H  +  HO. 
Sodium  silicate,  being  a  salt,  is  largely  ionized,  thus, 

Na2Si03  ?±  Na,Na,  +~Si03. 

Therefore,  the  hydrogen  ions  colliding  with  the  silicate 
ions  would  form  silicic  acid,  and  as  this  is  not  appreciably 
soluble  in  water,  it  soon  begins  to  separate  out  as  a  precipi- 
tate. This  continues  slowly  and  at  the  end  of  some  months 
even  an  inch  or  more  of  white,  gelatinous  silicic  acid  may 
be  found  at  the  bottom  of  the  jar.  At  the  same  time  the 
hydroxyl  ions  meeting  the  sodium  ions  form  sodium  hy- 
droxide, but  this  being  very  soluble  remains  largely  in 
the  form  of  ions  in  the  solution.  This  may  be  shown  by 
testing  with  red  litmus  paper;  it  is  also  noticeable  in 
its  effect  upon  the  hands,  giving  the  skin  a  slippery  feel- 


COMPOUNDS    OF   SILICON  299 

ing  as  alkalies  all  do.  Such  chemical  action  as  this  be- 
tween a  salt  and  water  is  called  hydrolysis,  from  two 
Greek  words,  meaning  decomposition  ~by  water.  Various 
other  cases  of  hydrolysis  will  be  studied  later.  In  reality 
the  action  of  water  upon  antimony  and  bismuth  salts,  ob- 
served in  the  preceding  chapter,  is  an  instance  of  hy- 
drolysis. 

Water  glass  is  also  used  as  a  cheap  cementing  mate- 
rial, in  many  cases  taking  the  place  of  glue.  This  is 
seen  in  the  manufacture  of  paper  boxes,  trunks,  and 
valises. 

6.  Crown  Glass. — When  lime,  sodium  carbonate  and 
silica  are  fused  together,   a  double  silicate   of  calcium 
and  sodium  is  formed  which  is  called  crown  glass.     Un- 
less very  pure  sand  is  used  there  will  be  small  quantities 
of  iron  present,  which  will  give  the  product  a  green  color. 
It  may  be  largely  removed  by  the  addition  of  some  oxi- 
dizing material  like  manganese  dioxide;  but  any  slight 
excess  of  this  compound  imparts  an  amethyst  color  to  the 
glass.     Crown  glass  has  a  relatively  low  melting  point ; 
hence,  it  may  easily  be  softened  in  the  Bunsen  burner. 
It  is  also  more  readily  attacked  by  alkalies  than  some 
other  varieties.     However,  on  account  of  its  cheapness  it 
is  used  for  all  ordinary  bottles,  for  common  window  glass, 
and  most  of  the  test  tubes  and  glass  tubing  used  in  the 
chemical  laboratory. 

7.  Bohemian    Glass. — When    potassium    carbonate    is 
fused  with  sand  and  lime  a  variety  known  as  Bohemian 
glass  is  obtained.     It  is  harder  than  crown  glass,  more 
transparent,  less  readily  attacked  by  chemical  reagents 
and  has  a  much  higher  melting  point.     It  is  commonly 
spoken  of  in  the  laboratory  as  "hard  glass."     It  is  used 
for  the  better  chemical  glassware — beakers,  flasks,  and  all 
sorts  of  other  apparatus.     The  better  grades  of  tumblers 


APPLIED    CHEMISTRY 

and  other  glassware  in  the  home  are  also  made  from  Bo- 
hemian glass. 

8.  Flint  Glass. — When  sand,  lead  oxide  and  silica  are 
fused  together,  a  variety  called  flint  glass  is  obtained. 
In  the  purest  form  it  is  sometimes  called  paste,  and  from 
it  are  made  the  imitation  or  paste  diamonds.    Flint  glass 
is  almost  perfectly  transparent,  is  very  soft  so  that  it  is 
easily  scratched,  and  has  high  refractive  power.    Most  op- 
tical lenses  are  made  from  it  on  account  of  the  ease  with 
which  it  is  cut,  its  brilliancy  and  high  refractive  power. 
It  is  the  last  property  that  gives  the  play  of  colors  seen 
in  the  imitation  diamonds,  almost  equal  to  the  genuine; 
but  the  softness  of  the  glass  soon  causes  a  loss  of  this 
power.     It  is  also  used  in  the  manufacture  of  cut  glass 
found  in  the  home. 

9.  Manufacture  of  Glass  Articles.— Tumblers  and  sim- 
ilar articles  of  household  use  are  molded.     A  sufficient 
amount  of  molten  glass  is -put  into  a  heated  mold  the  size 


Fig.    57. — Mold   for    making   glass    tumblers. 

and  shape  of  a  tumbler.  As  shown  in  Fig  57,  a  rod  de- 
scends, mechanically,  bearing  a  solid  but  smaller 
tumbler.  This  squeezes  the  molten  glass  into  the  space 


COMPOUNDS    OF   SILICON  301 

between  the  two  and  in  a  second  of  time  the  glass  is 
done.  Bottles  are  made  by  blowing.  A  suitable  amount 
of  molten  glass  is  taken  from  the  furnace  upon  the  end  of 
a  blowpipe.  (See  Fig.  58.)  This  is  placed  within  a  mold, 
and  by  lung  power  or  compressed  air  the  glass  is  blown 
until  it  issues  from  the  top  of  the  mold  in  the  form  of  a 


Fig.    58. — Mold    for    blowing   glass   bottles.      The    blow-pipe    with   molten    glass 
is   shown   hanging  within  the  opened  mold. 


large  bubble  and  bursts.  Immediately,  the  bottle  with  its 
ragged  top  in  placed  in  another  machine  which,  while 
the  glass  is  still  soft,  turns  it  round  and  round  until 
the  neck  and  top  are  perfectly  smooth.  Ordinary  win- 
dow glass  is  first  blown  into  long  cylinders.  These  are 
cut  lengthwise  and  flattened  out  while  still  hot,  just  as  a 


302  APPLIED    CHEMISTRY 

roll  of  paper  might  be  with  a  pair  of  scissors.  (See  Fig. 
59.)  Heavy  plate  glass  is  made  by  pouring  a  ladle  of  mol- 
ten glass  upon  a  table  and  immediately  rolling  until  it 
covers  the  top  of  the  table  and  has  attained  a  uniform 
thickness.  It  is  then  polished  by  revolving  discs  with 
water  and  pumice  or  some  similar  abrasive.  The  color  of 


Fig.    59. — Making   window   glass.      It   is   first   blown   into   form    of   a   cylinder. 
This    is   cut   open,   flattened   out  and   annealed. 


glass  articles  is  secured  by  the  introduction  of  small  quan- 
tities of  some  other  compound.  It  has  already  been  stated 
that  manganese  gives  an  amethyst  color;  cobalt  gives 
a  beautiful,  deep  blue;  copper  a  lighter  or  greenish  blue; 
chromium  a  clear,  beautiful  green;  calcium  fluoride  a 
translucent  white;  iron,  pale  green,  yellow  or  brown, 


COMPOUNDS  OF   SILICON  303 

according  to  the  kind  of  iron  salt  introduced;  gold  and 
some  copper  compounds  give  a  red  color. 

A  glass  rod  kept  soft  lay  heat  may  be  drawn  out  into 
thread  and  wound  like  silk  fibers  upon  a  large  wheel  or 
bobbin.  From  this  it  may  be  woven  into  various  articles 
such  as  ribbons,  bows  for  neckwear  and  even  into  cloth. 
Thus  used  it  has  the  sheen  of  satin,  but  naturally  it  is  not 
very  durable. 

10.  Annealing  Glass. — All  glass  articles  when  first 
made  are  very  brittle.  Annealing  consists  in  cooling 
them  so  very  slowly  that  the  molecules  are  enabled  to 
move  into  relatively  stable  positions.  This  is  done  by 
putting  the  articles  into  a  very  long  oven,  one  end  of  which 
is  extremely  hot.  They  are  then  very  slowly  moved 
mechanically  toward  the  cooler  end  and  after  several 
days  are  ready  for  packing  and  shipping. 

Exercises  for  Review 

1.  What  can  you  say  of  the  abundance  of  silicon  compounds  in 
nature  ? 

2.  Name  several  varieties  of  quartz. 

3.  Name   several  other  minerals   consisting    of    silica,    some    of 
\\hich  are  prized  for  their  beauty. 

4.  What  is  petrified  wood?     How  formed? 

5.  Give  the  characteristics  of  quartz. 

6.  Mention  some  uses  for  some  of  the  natural  forms  of  silica. 

7.  What  kind  of  an  oxide  is  silica?     What  acid  is  formed  theo- 
retically from  it? 

8.  How  is  water  glass  made?     In  what  form  is  it  used? 

9.  Give  method  of  preserving  eggs  with  water  glass. 

10.  Why  do  preserved  eggs  crack  when  boiled? 

11.  What   is   meant  by  hydrolysis?     Illustrate  by  means   of   so- 
dium silicate. 

12.  Name  two  cases  of  hydrolysis  in  a  preceding  chapter. 

13.  How  is  crown  glass  made?     Give  some  common  uses  for  it. 
Why  is  it  green  in  color?     How  may  this  be  removed? 


304  APPLIED    CHEMISTRY 

14.  From  what   is   Bohemian   glass  made?     Give  its   differences 
from  crown. 

15.  What   laboratory   uses   have   these   two   kinds   of   glass,   and 
why  ? 

16.  From   what   is   flint   glass  made?     Give   its   most  important 
uses.     Why  so  used?     What  use  has  it  in  our  homes? 

17.  Give  the  common  method  of  making  tumblers.     How  are  bot- 
tles made?     Plate  glass?     Window  glass? 

18.  What  is  meant  by  annealing?       How  is  it  done?     What  is 
really  accomplished  by  annealing? 


CHAPTER  XXV 

THE  ALKALI  METALS 

Outline — 

Comparison  of  the  Members 
Sodium 

(a)   Occurrence 

(fc)    Method  of  Preparing 

(c)   Characteristics 

(fZ)   Uses 

Compounds 

(«)    Sodium  Chloride 
(ft)    Sodium  Bicarbonate 

(c)  Sodium  Carbonate 

(d)  Sodium  Hydroxide 

(e)  Soap 
(/)   Borax 

(/7)   Hydrolysis  of   Compounds 
Potassium 

(a}   Occurrence 
(1}   Characteristics 
Compounds 

(a)   Potassium  Carbonate 
(6)   Potassium  Hydroxide 

(c)  Potass'um  Nitrate 

(d)  Potassium  Chlorate 
(e~)   Other  Compounds 

1.  General  Comparison. — This  group  includes  the  most 
strongly  positive  metals,  as  the  halogen  group  does  the 
most  strongly  negative.  They  occupy  a  position  at  the 
left  end  of  the  periodic  table  while  the  halogens  are 
at  the  extreme  right.  The  two  important  members  are 
sodium  and  potassium;  the  other  three,  lithium,  caesium 
and  rubidium,  are  much  less  common.  More  or  less 
vigorously  they  all  decompose  water,  forming  strong 

305 


306  ,    APPLIED    CHEMISTRY 

bases  or  alkalies,  for  which  reason  they  are  commonly 
called  the  alkali  metals. 

.  2.  Occurrence  of  Sodium. — Common  salt  is  one  of  the 
most  familiar  of  all  substances.  It  occurs  in  small 
quantities  in  nearly  all  soils;  it  is  present  in  the  dust 
particles  floating  in  the  air;  it  is  the  sodium  in  this 
compound  which  colors  a  flame  yellow  when  a  room  is 
being  swept.  A  clean  platinum  wire,  drawn  through 
the  fingers,  in  a  Bunsen  flame  will  give  the  characteristic 
yellow  coloration.  It  is  found  in  the  blood  to  the  extent 
of  0.8  per  cent.  About  seven-tenths  of  the  solid  matter 
found  in  sea  water,  or  nearly  3  per  cent  by  weight,  is 
common  salt,  and  amounts  to  the  astonishing  sum  of  over 
35,000  billion  tons.  Some  one  has  calculated  that  on  the 
basis  of  an  average  depth  of  1,000  feet,  the  common  salt 
in  the  various  oceans  would  occupy  a  bulk  of  3,500,000 
cubic  miles  and  that  if  this  were  separated  out  and  piled 
up  it  would  make  a  mountain  range  rivaling  in  height 
and  length  some  of  our  great  western  chains.  In  some 
of  the  Middle-West  States,  notably,  Kansas,  deposits 
of  nearly  pure  salt  are  known,  300  feet  in  thickness,  cov- 
ering vast  areas.  Likewise,  New.  York,  Ohio  and  Mich- 
igan have  extensive  deposits  and  these  three  states  to- 
gether with  Kansas  furnish  about  nine-tenths  of  all  the 
salt  made  in  the  United  States.  California,  Utah,  West 
Virginia,  Pennsylvania,  Louisiana,  Texas  and  Oklahoma 
also  produce  considerable  amounts.  In  California  one 
or  more  lakes  covering  an  area  of  from  30  to  50  square 
miles  are  known,  saturated  with  salt:  a  crust  6  to  8 
inches  in  thickness  of  nearly  pure  salt  covers  the  surface 
over  which  in  the  dry  season  anyone  may  walk  with 
safety.  These  lakes  glisten  in  the  sun  like  one  in  our 
northern  climates,  frozen  over  and  covered  with  snow. 
Chile  saltpeter,  NaN03,  is  another  abundant  natural 


THE   ALKALI    METALS  307 

compound  but  not  so  widely  distributed  as  common  salt. 
It  is  found  mostly  in  the  desert  areas  of  Chile,  covering 
about  450  square  miles  or  about  the  size  of  a  single 
county  in  some  of  the  Middle-West  states.  The  deposits 
are  from  25  to  50  per  cent  sodium  nitrate  and  something 
like  5  feet  in  thickness,  while  the  quantity  is  consider- 
able it  is  far  from  unlimited.  Other  natural  compounds 
of  sodium  are  known,  but  they  are  unimportant. 

3.  Preparation  of  Sodium. — Sir  Humphrey  Davy,  in 
1807,  first  prepared  the  metal  by  the  electrolysis  of  so- 
dium hydroxide.  At  the  present  time  the  same  method 
is  used,  improved,  and  known  as  the  Castner  process. 
Fig.  60  gives  an  idea  of  the  apparatus.  The  sodium  hy- 


Fig.    60. — Preparation    of    sodium,  by    the    Castner    process. 

droxide  is  melted  in  a  vessel,  marked  V,  usually  made 
of  cast  iron ;  to  this  is  attached  the  cathode  in  the  form 
of  a  bundle  of  carbon  rods.  The  anode,  marked  W,  is 
a  vessel,  similar  to  V,  inverted  over  and  dipping  into 
the  melted  caustic  soda.  In  the  center,  the  vessel,  P, 
which  reaches  down  below  the  upper  end  of  the  carbon 
rods  is  the  receiver  for  the  sodium  and  is  closed  at  the 
bottom  by  a  coarse  wire  gauze.  The  current  causes  the 
sodium  and  hydrogen,  both  positive,  to  collect  upon  the 
carbon  rods,  from  which  they  rise  to  the  top  within 
the  vessel,  P.  The  hydrogen  escapes  and  the  sodium 
when  cooled  is  removed  and  molded  into  sticks.  The 


308  APPLIED    CHEMISTRY 

oxygen  collects  upon  the  vessel,  W,  which  is  the  anode, 
from  which  it  may  be  drawn  off  or  allowed  to  bubble 
out  and  escape. 

4.  Characteristics. — Sodium  is  a  silvery-white  metal, 
at  ordinary  temperatures  soft  and  pliable.  It  reacts 
vigorously  with  water  and  must  be  kept  under  naphtha 
or  some  hydrocarbon  oil  free  from  oxygen.  Exposed 
to  the  air  it  rapidly  attracts  the  moisture,  with  which  it 
reacts  and  forms  sodium  hydroxide.  This  in  turn  ab- 
sorbs the  carbon  dioxide  and  forms  sodium  carbonate, 
so  that  ultimately  the  metal  when  exposed  to  the  air 
becomes  a  white,  brittle  mass.  On  a  vessel  of  water  at 
room  temperature  a  piece  of  sodium  rolls  about,  grad- 
ually diminishing  in  size,  until  it  finally  disappears.  On 
warm  or  hot  water  the  heat  generated  is  sufficient  to 
ignite  the  hydrogen  evolved  and  volatilize  small  portions 
of  the  sodium  which  color  the  flame  yellow.  On  wet 
blotting  paper,  a  small  bit  of  sodium,  not  able  to  roll 
around,  soon  becomes  hot  enough  to  melt,  at  a  tempera- 
ture but  little  below  the  boiling  point  of  water,  96°  C. 
It  is  then  a  silvery  globule  like  mercury ;  if  dropped 
upon  the  floor  at  this  point  it  breaks  into  numerous 
smaller  globules  Avhich  burn  with  the  usual  yellow  flame 
as  they  roll  off  in  all  directions.  The  irritating  white 
fumes  which  arise  as  the  metal  thus  burns  are  sodium 
peroxide,  Na202.  Sodium  is  soluble  in  mercury,  and  if 
present  in  sufficient  quantity  forms  a  solid  amalgam, 
an  alloy  of  which  one  constituent  is  mercury.  This 
readily  decomposes  water,  but  less  rapidly  than  sodium 
alone.  The  fact  is  made  use  of  in  the  electrolytic  process 
of  making  chlorine  described  on  p.  122.  Sodium  may  be 
converted  into  vapor  at  about  750°  C.  The  density  of  the 
vapor  shows  it  to  be  monatomic.  When  heated  sodium 
combines  readily  with  both  oxygen  and  chlorine ;  the  oxy- 


THE    ALKALI    METALS  300 

gen  compound  thus  obtained  is  the  peroxide,  spoken  of 
elsewhere  as  "oxone"  used  in  preparing  oxygen. 

5.  Uses. — Sodium  lias  no  commercial  uses.     In  drying 
some  organic  compounds  and  in  some  other  laboratory 
work  it  is  of  value.    The  preparation  of  artificial  rubber, 
still  in  the  experimental  stage,  employs  sodium  in  one 
step  of  the  process. 

6.  Compounds. — The  occurrence  of  sodium  chloride  in 
nature  has  already  been  mentioned.    It  is  obtained  from 
these   sources  in   two   or   three   ways.     A   very   consid- 
erable amount   is   mined   as  any   other  mineral.     Since 
more  or  less  insoluble  foreign  matter  usually  accompan- 
ies this  rock  salt  as  it  is  called,  it  is  largely  used  for 
stock,  or  crushed  to  coarse  grains  for  making  freezing 
mixtures    for   refrigeration    and    for    keeping    ices    and 
creams.     At  Salt  Lake,  Utah,  the  water,  already  satu- 
rated, is  pumped  into  basins  and  evaporated  by  the  heat 
of  the  sun.     The  product  is  somewhat  impure  but  suita- 
ble for  refrigeration  and  for  packing  purposes.     At  San 
Francisco  the  A\7ater  is  pumped  likewise  into  basins  and 
evaporated.     Most  of  the  salt  used  upon  the  table  and 
in  food  products  is  obtained  from  salt  wells.     These  are 
drilled  down  to  reach  the  layer  of  salt,  water  is  run  in 
and    allowed    to    remain    until    saturated.      It    is    then 
pumped  out  and  after  any  insoluble  matter  has  settled 
out,  it  is  evaporated  and  crystallized. 

7.  Characteristics  of  Salt. — Salt  obtained  from  wells 
is  comparatively  pure.    Usually  it  contains  a  very  small 
percentage   of   magnesium   chloride   which,   being   deli- 
quescent, causes  the  whole  mass  to  become  damp  in  wet 
weather.     If  a  stream  of  hydrogen  chloride  be  passed 
through  a  saturated  solution  of  salt,  pure  sodium  chlo- 
ride will   separate   out  in  fine   crystals.     As   the   mag- 
nesium  chloride   contained   is   usually  less   than   1/2   of 


310 


APPLIED    CHEMISTRY 


1  per  cent  and  most  of  the  samples  of  salt  upon  the  mar- 
ket assay  from  97  to  99  per  cent  in  purity,  it  is  not  nec- 
essary, except  for  some  chemical  purposes,  to  purify  the 
commercial  supply.  At  the  present  time  several  brands 
of  table  salt  may  be  obtained  which  do  not  cake  in 
damp  weather.  They  have  not  been  freed  from  the  mag- 
nesium chloride,  but  have  had  some  finely  powdered  sub- 
stance like  starch  or  cooking  soda  or  prepared  chalk 
in  very  small  amounts  intimately  mixed  with  the  salt, 


us* 


Fig.    61. — Preparation    of   salt    in    San    Francisco    Bay,   by    evaporation    of    sea 

water. 

so  that  the  individual  grains  are  protected  from  the  air 
by  a  thin  coating  of  the  powder.  It  will  probably  be 
found,  if  the  label  upon  the  container  is  read,  that  the 
adulterant  used  will  be  stated.  As  the  substance  thus 
employed  is  harmless  and  always  in  very  small  propor- 
tions, it  cannot  be  said  to  be  especially  objectionable. 
Upon  the  lower  organisms  salt  is  altogether  destructive. 
Such  is  the  explanation  of  its  preservative  qualities. 
Sprinkled  upon  such  soft  bodied  animals  as  snails  and 


THE   ALKALI    METALS  oil 

slugs,  which  in  some  parts  of  our  country  grow  to  great 
size,  salt  seems  to  extract  the  moisture  from  the  body.  It 
shrinks  rapidly  in  size,  and  the  animal  soon  dies.  In  large 
amounts  it  is  harmful  to  the  human  body,  and  in  some 
countries  has  been  frequently  used  as  a  means  of  suicide. 
In  small  quantities  it  is  regarded  not  only  as  not  harmful 
but  even  necessary  for  the  body,  to  provide  the  hydrochlo- 
ric acid  needed  in  digestion.  Undoubtedly,  however, 
nearly  everyone  uses  much  more  than  necessary,  so  that 
it  must  be  eliminated  by  the  skin  in  the  perspiration  and 
through  other  excretory  organs. 

8.  Uses. — It  is  said  that  about  11  pounds  per  capita  of 
refined  salt  is  used  every  year  in  the  United  States  in  the 
seasoning  of  foods.    Much  more  is  employed  in  the  pres- 
ervation of  meats  and  meat  products.     Altogether,  sta- 
tistics  show   that   the   total   quantity   used   every   year 
in  various  ways  amounts  to  30,000,000  barrels,  more  than 
a  barrel  for  every  family  of  four  individuals.     Besides 
these  uses,  so  familiar  to  all,  salt  forms  the  starting  point 
in  the  manufacture  of  several  very  important  compounds 
which  will  be   studied  later. 

9.  Sodium  Bicarbonate. — This  compound,   chemically 
known  as  acid  sodium  carbonate  with  formula  NaHCOo,, 
is  common  cooking  soda.     The  word  'bicarbonate  means 
twice  carbonated,  and  was  so  given  because  the  compound 
was  formerly  prepared  by  passing  a  stream  of  carbon  di- 
oxide  into   a  solution   of   sodium   carbonate,   whereupon 
the  bicarbonate,  being  much  less  soluble,  crystallized  out. 
Thus  it  was  obtained  by  carbonating  sodium  carbonate. 
The  equation  shows  the  reaction, 

C02  +  Na2CO,  +  H20  -»  2NaHC03. 

At  the  present  time  the  commercial  supply  is  made  by 
what  is  known  as  the  Solvay  process.  A  saturated  solu- 


312  APPLIED    CHEMISTRY 

tion  of  salt  is  treated  with  ammonia  and  carbon  dioxide 
when  three  reactions  take  place,  thus, 

NH3  +  H20  -»  NH4HO, 
NH4HO  +  C02  ->  NH4HC03, 
NaCl  +  NH4HC03  ->  NaHC03  +  NH4C1. 

A1 .  the  acid  carbonate  is  not  very  soluble  in  water  it  crys- 
tallizes, after  which  it  is  removed,  dried  and  pulverized, 
usually,  for  the  commercial  supply.  The  ammonium  chlo- 
ride solution  is  saved,  treated  with  lime  and  heated, 
whereupon  the  ammonia  is  recovered  to  be  used  again 
in  the  first  step  of  the  process.  It  will  be  seen,  there- 
fore, that  the  manufacture  is  very  cheap, 

2NH4C1  +  CaO  ->  CaCl2  +  2NH3  +  H20. 

10.  Sodium  Carbonate. — The  greater  portion  of  the 
acid  carbonate  made  by  the  Solvay  process  is  converted 
into  the  normal  carbonate  by  heating,  thus, 

2NaHC03  -»  Na2C03  +  H20  +  C02. 

The  carbon  dioxide  thus  obtained  is  used  in  the  first 
step  of  the  process  described  above  for  making  sodium 
bicarbonate,  which  still  further  cheapens  the  process. 
Another  method,  known  as  the  Leblanc  process,  was 
used  for  many  years.  This  consisted  in  the  conversion 
of  common  salt  into  sodium  sulphate  by  strongly  heat- 
ing with  sulphuric  acid  during  which  reaction  hydrogen 
chloride  was  evolved.  (See  p.  126.)  By  further  treat- 
ment of  the  sodium  sulphate  thus  obtained  with  coke  and 
limestone  the  sulphate  was  converted  into  a  carbonate 
which  was  separated  from  the  mixture  by  dissolving 
in  water.  The  process  is  much  more  complicated  and 
expensive  than  the  Solvay  and  would  now  be  abandoned 
were  it  not  for  the  by-product  obtained,  hydrochloric 
acid.  By  the  Solvay  process  anhydrous  sodium  carbonate 


THE    ALKALI    METALS  313 

is  obtained;  by  the  Leblanc,  the  hydrate,  Na,CO,  .  10H,0. 
This  is  known  as  sal  soda  or  washing  soda.  It  is  strongly  ^ 
efflorescent  and  when  exposed  to  the  air  rapidly  loses 
nine  of  the  water  molecules  contained.  Heat  is  necessary 
to  remove  the  remainder.  Sodium  carbonate  is  a  neutral 
salt,  yet,  dissolved  in  water,  it  gives  an  alkaline  reaction 
with  litmus.  This  is  explained  in  the  same  way  as  in  the 
case  of  the  water  glass,  p.  298.  The  sodium  carbonate 
in  water  is  largely  ionized,  thus, 

Na2C03<=>Na,  Na  +  C03. 
Water  forms  some  few  ions, 

H20  ?=±  H  +HO. 

The  hydrogen  ions  reacting  with  the  carbonate  ions  pro- 
duce carbonic  acid.  This,  however,  is  an  exceedingly 
weak  acid,  and,  as  is  true  of  all  weak  acids,  is  very  slightly 
ionized,  hence  exists  almost  entirely  in  the  molecular 
form.  The  hydroxide  ions  reacting  with  the  sodium  form 
sodium  hydroxide,  which  being  a  very  strong  base  is 
largely  ionized.  Thus  a  very  considerable  amount  of  hy- 
droxide ion  is  always  present  in  such  a  solution.  As  the 
alkali  reaction  is  due  to  the  presence  of  hydroxide  ions 
a  solution  of  sodium  carbonate  always  turns  litmus  paper 
blue. 

11.  Further  Study  of  Hydrolysis. — As  stated  above 
the  alkaline  reaction  of  sodium'  carbonate  is  due  to  hy- 
drolysis. It  is  of  such  importance  as  to  merit  further 
study.  Common  salt  dissolved  in  water  shows  no  litmus 
reaction.  The  reason  may  be  seen  by  writing  the  ionic 
reactions, 

NaCl  *±  Na  +  Cl 


314  APPLIED    CHEMISTRY 

When  the  ions  present  react,  two  new  products  form, 
NaHO  and  HCL  As  one  is  a  strong  base  and  the  other 
a  strong  acid  they  give  relatively  equal  quantities  of 
hydrogen  and  hydroxide  ion  and  hence  neutralize  each 
other  so  that  there  is  no  litmus  reaction.  If  sodium 
sulphate  be  used,  like  results  are  obtained, 

Na2S04^Na,  Na  +  S04, 

H20  <=±  H  +  HO. 

The  new  products  are  sulphuric  acid  and  sodium  hy- 
droxide, both  strong.  Again  the  hydrogen  ions  and  hy- 
droxide ions  practically  neutralize  each  other  and  there 
is  no  litmus  reaction.  This  is  true  of  all  salts  formed 
by  the  union  of  a  strong  base  and  a  strong  acid.  It  is 
usually  stated  thus:  Salts  formed  by  the  union  of  a  strong 
base  uniting  with  a  strong  acid  are  not  hydrolyzed  appre- 
ciably in  water. 

Salts  like  sodium  carbonate  and  sodium  silicate  are 
the  result  of  the  union  of  a  strong  base  and  a  weak  acid 
and  give  alkaline  reaction.  Conversely,  salts  formed  from 
a  weak  base  and  a  strong  acid  give  an  acid  reaction.  This 
will  be  evident  if  the  ionic  equations  are  written, 

FeCl3  ?±  Fe*+Cl,  Cl,  Cl, 

H20?±H-HO. 

The  new  products  formed  are  hydrochloric  acid  and  ferric 
hydroxide.  The  acid  is  very  strong,  while  the  base  is 
weak;  obviously,  therefore,  the  litmus  reaction  will  be 
acid  in  character. 

CuS04  *±  Cu  +  S04. 

H20  *±  H  +  HO. 
In  the  above  solution  the  base  formed  will  be  copper  hy- 


THE    ALKALI    METALS  315 

droxide  which  is  weak  and  the  acid  sulphuric  which  is 
strong.  Again  the  litmus  reaction  will  be  acid.  All  such 
salts  behave  in  a  similar  manner.  This  case  is  usually 
expressed  thus:  Salts  formed  by  the  union  of  a  weak  base 
rvith  a  strong  acid,  or  conversely,  by  the  union  of  a  strong 
base  with  a  weak  acid  are  partially  hydrolyzed.  They 
give  an  acid  or  alkaline  reaction  according  as  the  acid  or 
the  base  is  the  strong  factor. 

There  is  a  third  class  of  salts  formed  by  the  union  of  a 
weak  base  with  a  weak  acid.  Such  are  ferric  carbonate 
and  aluminum  sulphide.  lonically  written,  ferric  car- 
bonate gives 

Fe2(C03)3?±Fe,  Fe  +  CO3  +  C03  +  C0 


3, 


The  ferric  ions  collide  with  the  hydroxide  ions  and  give 
ferric  hydroxide  ;  likewise,  the  hydrogen  and  carbonate 
ions  form  carbonic  acid.  Both  compounds  are  ionized 
very  slightly.  The  result  is  the  molecules  accumulate  ; 
the  solution  becomes  saturated  with  carbonic  acid  and  at 
once  it  begins  to  decompose  with  the  escape  of  carbon 
dioxide,  thus, 

H2C03  -»  H20  +  C02. 

Thus  the  carbonate  ions  are  constantly  forming  mole- 
cules of  carbonic  acid  and  this  is  being  destroyed  by  the 
escape  of  the  carbon  dioxide,  so  that  it  is  removed  from 
the  sphere  of  action.  Likewise,  the  ferric  hydroxide,  not 
being  appreciably  soluble  in  water,  begins  to  form  a  pre- 
cipitate and  it  also  is  removed  from  the  sphere  of  reac- 
tion. The  ultimate  result  is  that  practically  all  the  car- 
bon dioxide  escapes  and  the  ferric  ions  have  formed  fer- 
ric hydroxide  which  alone  remains  as  a  precipitate.  In 
other  words,  ferric  carbonate  in  water  has  been  converted 
entirely  into  ferric  hydroxide,  that  is  completely  decom- 


316  APPLIED    CHEMISTRY 

posed.  The  conclusion  is  usually  stated  thus:  Com- 
pounds formed  by  the  union  of  a  weak  base  with  a  weak 
acid  in  water  are  completely  hydrolyzed.  The  action  of 
one  class  of  baking  powders  depends  upon  this  very 
fact  and  will  be  taken  up  at  another  time. 

12.  Uses  of  Sodium  Carbonate. — Its  chief  use  is  for 
the  manufacture  of  other  compounds.     With  silica  it  is 
used  in  making  two  varieties  of  glass;  it  is  also  used  in 
preparing   sodium   hydroxide,    a   very   important    com- 
pound to  be  studied  later.     It  is  used  extensively  in  soft- 
ening water  and  is  the  chief  constituent  of  most  wash- 
ing powders.     In  addition,  these  may  contain  powdered 
caustic  soda,  borax,  pumice  stone,  soap  powder,  sodium 
peroxide,  and  possibly  sometimes  some  other  substances. 
Scouring  powders  usually  contain  pumice;  if  put  into 
a  glass  of  water  and  stirred  the  other  ingredients  will 
dissolve  leaving  the  pumice  as  a  gray  deposit.     "  Dutch 
Cleanser"  is  a  washing  powder  of  this  kind.     They  are 
excellent  in  their  way,  but  should  not  be  used  on  highly 
polished  surfaces  such  as  silverware  and  the  like. 

13.  Sodium   Hydroxide. — This   compound,    NaHO,    is 
commonly  called  caustic  soda.    In  an  impure  form  it  is 
frequently  sold  at  groceries  under  the  name  of  "lye." 
Much  of  it  is  prepared  from  sodium  carbonate  by  treat- 
ing it  with  slaked  lime  thus, 

Ca(HO)2  +  Na2C03  -»  CaC03  +  2NaHO. 

The  calcium  carbonate  is  not  soluble  in  water,  hence 
forms  a  precipitate  from  which  the  caustic  may  be 
drained  off.  A  considerable  amount  of  sodium  hydrox- 
ide is  also  made  electrolytically  as  described  under 
chlorine.  Made  thus  it  is  much  more  apt  to  be  pure 
than  by  the  other  process;  in  fact,  commercial  caustic 


THE   ALKALI    METALS  317 

soda  made  from  sodium  carbonate  often  contains  as 
much  as  25  per  cent  of  the  latter  compound  or  other  im- 
purities. For  most  of  its  uses  such  impurities,  however, 
are  not  especially  objectionable.  To  obtain  pure  caus- 
tic soda  from  this  commercial  variety  it  is  dissolved  in 
alcohol,  filtered  and  the  solvent  evaporated.  The  im- 
purities do  not  dissolve  in  the  alcohol,  hence  are  left 
behind  in  the  filtration. 

14.  Characteristics    of    Sodium   Hydroxide. — It    is    a 

white  solid :  the  pure  caustic  is  usually  sold  in  the  form 
of  small  sticks  although  it  may  be  had  in  a  powder.  The 
commercial  variety  is  usually  powdered.  It  is  exceed- 
ingly caustic  when  moist,  and  is  very  deliquescent.  Ex- 
posed to  the  air  it  rapidly  dissolves  in  the  moisture 
present,  takes  up  carbon  dioxide,  and  ultimately,  as 
stated  in  the  case  of  sodium,  forms  solid  sodium  car- 
bonate. 

15.  Uses. — As  already  stated  caustic  soda  is  a  constit- 
uent of  many  washing  powders.    It  is  used  in  the  manu- 
facture of  paper  pulp,  in  decomposing  the  woody  fiber; 
also  in  many  other  manufacturing  processes.     Probably 
its  most  extensive  use  is  in  the  manufacture  of  soap. 

16.  Soap. — Soap   is   a   salt   which   in  water   gives   an 
alkaline  reaction  because  of  hydrolysis.     It  is  prepared 
by  treating  some  fat  or  oil  with  caustic  soda.    The  reac- 
tion is  shown  by  the  following  equation, 

3\alIO  -I-  CaTT3(C17II3rjCOO)3  -» 

3NaC17H,,COO  +  C3II5(HO)3. 

Stearin  has  been  used  here  as  typical  of  the  other  fats. 
It  will  be  noted  that  glycerine  is  the  by-product.  On 
a  large  scale,  soaps  are  generally  made  from  the  waste 
fats,  or  those  of  animals  condemned  by  inspectors  at 


318  APPLIED    CHEMISTRY 

the  packing  houses  as  unfit  for  food,  and  from  other 
similar  sources;  also  from  some  of  the  cheaper  oils.  The 
yellow  rosin  soaps  usually  contain  considerable  rosin 
substituted  for  a  portion  of  the  fat.  The  chemical  proc- 
ess in  the  making  of  soap  is  called  saponification.  Chem- 
ical reaction  with  organic  compounds  is  nearly  always 
slow,  for  the  reason  that  they  are  not  ionized.  Hence, 
three  or  four  days  of  constant  -boiling  are  necessary  for 
the  completion  of  the  process.  At  the  end  of  this  time, 
salt  is  added,  which  causes  a  more  perfect  separation  of 
the  salt  and  glycerine.  The  salt  water  with  the  glycerine 
is  drawn  off  beneath  the  soap  layer,  evaporated  until  of 
such  concentration  that  the  salt  will  crystallize  out,  after 
which  the  glycerine  is  concentrated  in  "vacuum  pans" 
under  partial  air  pressure.  If  potassium  hydroxide  is 
used  instead  of  sodium,  a  soft  soap  is  obtained  in  which 
the  glycerine  remains  dissolved.  In  small  quantities  it 
is  prepared  for  use  in  pharmacy,  from  pure  fats  or  oils, 
especially  linseed.  Formerly,  practically  all  the  soap  used 
by  those  living  in  the  country  was  home-made.  The  ashes 
obtained  during  the  winter  months  were  put  into  hoppers 
and  kept  dry.  In  the  spring  lime  was  added  and  the  mix- 
ture leached  with  water,  added  in  small  quantities  at  a 
time.  These  reactions  took  place, 

CaO  +  H20  ->  Ca(HO)2, 

Ca(HO)2  +  K2COa  ->  CaCO3  +  2KHO. 

The  water,  which  slowly  trickled  from  the  hopper,  con- 
tained the  potassium  hydroxide  and  was  called  lye.  It 
was  then  boiled  in  large  iron  kettles  with  any  waste  fats 
that  had  accumulated  during  the  winter.  If  hard  soap 
was  desired,  when  saponification  was  complete,  salt  was 
added  and  the  whole  allowed  to  cool.  The  soap  floated 
on  the  spent  lye  and  when  cold  could  be  lifted  off  and  cut 


THE   ALKALI    METALS  319 

into  cakes.  Made  thus  it  is  always  brown  in  color  and 
usually  contains  more  or  less  free  alkali.  Since  soap  is 
a  salt  made  by  the  union  of  a  strong  base  and  a  weak  acid, 
in  water  owing  to  hydrolysis,  it  will  give  an  alkaline 
reaction  even  if  there  be  no  free  alkali  contained.  To 
determine  whether  the  sample  be  devoid  of  free  alkali, 
some  of  it  must  be  dissolved  in  alcohol  which  does  not 
cause  hydrolysis.  A  strong  alkaline  test  in  such  a  solu- 
tion indicates  free  alkali  in  the  soap.  Floating  soaps  are 
produced  partly  by  forcing  minute  bubbles  of  air  into 
the  soap  before  -it  is  made  into  cakes  and  partly  by  the 
removal  of  much  of  the  water  present.  They  are  more 
durable  than  soaps  containing  much  water,  although 
possibly  a  little  slower  in  producing  a  "suds"  or  lather. 
Transparent,  glycerine  soaps  are  made  by  dissolving 
ordinary  soap  in  alcohol  and  filtering  out. the  insoluble 
residue ;  the  alcohol  is  recovered  by  distillation.  Such 
soaps  are  expensive  because  of  the  added  labor  in  prepar- 
ing them  and  also  from  the  fact  that  they  dissolve  rapidly 
in  water  and  hence  do  not  last  well.  Many  soaps  contain 
fillers,  that  is  substances  like  sodium  carbonate  or  water 
glass  worked  in  by  "crutchers. "  These  consist  of  a 
large  endless  screw  like  an  augur  fitting  somewhat  loosely 
within  a  large  upright  cylinder.  The  warm,  pasty  soap 
is  run  into  these,  the  filler  added  and  the  screw  started. 
In  the  course  of  several  hours  the  whole  is  thoroughly 
mixed.  Some  of  these  fillers,  especially  sodium  carbonate, 
are  not  particularly  objectionable,  but  the  value  of  the 
water  glass  is  doubtful.  All  of  them  cheapen  the  cost 
of  the  soap  to  the  manufacturer.  From  the  crutchers 
the  soap  is  run  into  large  molds  holding  several  hundred 
pounds,  where  it  hardens.  It  is  removed  from  these,  al- 
lowed to  dry  several  weeks,  is  then  cut  into  bars,  pressed 


320  APPLIED   CHEMISTRY 

into  cakes  by  machinery,  wrapped  and  packed  almost  en- 
tirely without  the  touch  of  a  human  hand. 

17.  Sodium  Nitrate,  NaN03. — This  compound  is  known 
commercially  as  Chile  saltpeter,  and  has  been  mentioned 
elsewhere.     It  is  a  white,  crystalline  solid,  used  for  the 
manufacture  of  gunpowder,  nitric  acid  and  extensively 
as  a  fertilizer. 

18.  Borax. — Chemically,  borax  is  sodium  tetraborate, 
Na2B407  .  10H20.     Our  supply  is  obtained  principally 
from  the  deposits  of  calcium  borate  in  California.    This 
natural  compound  is  treated  with  sodium  carbonate  with 
the  following  reaction, 

CaB407  +  Na2C03  ->  CaCOs  +  Na2B407. 

The  mixture  is  treated  with  hot  water  which  dissolves 
out  the  borax,  but  not  the  calcium  carbonate.  When 
crystallizing  the  salt  takes  up  ten  molecules  of  water. 
It  is  a  white  solid,  somewhat  efflorescent,  giving  an  alka- 
line reaction  in  water  due  to  partial  hydrolysis.  It  is 
used  in  many  washing  powders,  but  is  more  expensive 
than  sal  soda.  Small  quantities  are  used  in  the  chemi- 
cal laboratory  in  testing  for  various  metals.  When  fused 
in  a  loop  on  the  end  of  a  platinum  wire,  it  loses  its 
water  of  combination  and  forms  a  perfectly  transparent 
glass ;  now,  if  this  is  dipped  into  a  solution  of  certain  met- 
als and  again  fused,  or  if  a  minute  portion  of  certain  ox- 
ides be  fused  with  it,  it  forms  beautifully  colored  "beads" 
which  are  distinctive.  For  example,  cobalt  gives  a  deep 
blue ;  nickel  a  brown ;  chromium  a  bright  emerald  green ; 
manganese,  amethyst.  It  is  commonly  used  in  hard 
soldering  as  a  flux.  There  is  always  a  film  of  oxide  more 
or  less  thin  upon  the  surface  of  nearly  every  metal.  If 
solder  is  poured  upon  such  a  surface  it  will  not  adhere 
because  it  does  not  really  come  in  contact  with  the 


THE   ALKALI    METALS  321 

metal.  When  borax  is  applied,  it  melts,  at  the  tem- 
perature necessary  for  doing  the  work,  dissolves  the  thin 
film  of  oxide,  and  leaves  a  perfectly  clean  metal  to 
which  the  solder  strongly  adheres. 

19.  Occurrence  of  Potassium. — The  third  member  of 
the  sodium  group  in  point  of  density  is  potassium  with 
an  atomic  weight  of  39.     It  is  found  in  several  natural 
compounds,    but    much   less    abundantly    than    sodium. 
The  most  common  is  potassium  chloride,  mixed  usually 
with  magnesium  chloride.    Most  salt  lakes  contain  small 
quantities  of  both  potassium  and  magnesium  chloride. 
The  presence  of  magnesium  chloride  in  table  salt  has 
already  been  mentioned.     As   these   two   chlorides   are 
much  more   soluble   in  water  than   common   salt,   they 
will  remain  in  solution  until  most  of  the  sodium  chloride 
has  already  crystallized  out,    Thus,  in  the  famous  Stass- 
furt   deposits   of   Germany,    the   lower   portions,    many 
hundreds  of  feet  in  thickness,  are  common  salt,  while 
the  upper  layers  contain  much  potassium  and  magne- 
sium chloride.     Probably  the  same  will  be  found  true 
when  the  Great  Salt  Lake  in  Utah  and  other  similar 
lakes  in  this  country  have  finally  become  dry.     At  pres- 
ent, the  portion  separating  out  is  largely  sodium  chlo- 
ride, while  the  water  still  contains  the  greater  part  of  the 
magnesium  and  potassium   compounds.     Potassium  ni- 
trate is  also  found  in  nature,  but  not  in  such  quantities 
as  the  sodium  nitrate  beds  of  Chile. 

20.  Preparation  of  Potassium. — Potassium   was   first 
prepared  by  Davy  by  the   same   method   he   used   for 
making  sodium,  and  in  the  same  year.    Later,  for  many 
years  the   commercial   supply   was  obtained   by   heating 
potassium  hydroxide   with   carbon.      Now,   however,   it 
is  made   electrolytically   by   a   process   similar   to   that 
of  sodium. 


322  APPLIED    CHEMISTRY 

21.  Characteristics  of. — Potassium  is  a  silvery-white 
metal,  lighter  than  water,  with  a  melting  point  of  about 
63.     Small   quantities   of   the   metal   volatilized   in   the 
Bunsen  flame  give  a  violet  color.     This  generally  serves 
as  the  test  for  potassium  salts,  just  as  the  yellow  flame 
does  for  sodium.     The  vapor  of  potassium  is  green  in 
color.     The  density  of  the  vapor  shows  that  it  is  monat- 
omic.       It  reacts  vigorously  with  water  even  if  cold, 
with  the  evolution  of  sufficient  heat  to  ignite  the  hydro- 
gen set  free.     Sufficient  of  the  metal  is  always  at  the 
same  time  volatilized  to  color  the  flame  decidedly  vio- 
let.    The  following  equation  shows  the  reaction, 

2K  +  2II20  ->  H2  +  2KHO. 

Exposed  to  the  air  reactions  similar  to  those  in  the 
case  of  the  sodium  occur  with  the  ultimate  formation  of 
potassium  carbonate.  It  must,  therefore,  like  sodium, 
be  preserved  in  some  oil  like  naphtha  which  contains  no 
oxygen.  Outside  the  chemical  laboratory  potassium  has 
little  use. 

22.  Potassium  Carbonate,  K2C08. — Years  ago  consid- 
erable quantities  of  this  salt  were  obtained  from  wood 
ashes.     From   their   treatment   in  large   iron   pots,   the 
salt  extracted  by  the  water  came  to  be  known  as  pot- 
ashes, and  later  as  potash,  from  which  the  name  of  the 
metal  was  derived.     Since   the   disappearance   of  many 
of  the  original  great  forests?  this  source  has  become  neg- 
ligible.    At  the  present  time,  sugar  beets  furnish  a  very 
considerable  amount.     The  sap  is  boiled  down  in  vacuum 
pans  to  the  point  at  which  the  crystallizablc  sugar  will 
separate   out ;   the   portion  which  will  not   crystallize  is 
known  as  molasses  and  is  separated  from  the  sugar  by 
centrifugal  machines.     The  molasses  is  fermented  with 
yeast  and  made  into  alcohol.    From  the  residue  the  potas- 


THE   ALKALI    METALS  323 

slum  carbonate  is  obtained.  Another  source  of  consider- 
able potassium  carbonate  is  the  wool  of  sheep.  An  oily 
substance  called  siiint  which  sometimes  equals  the  weight 
of  the  clean  wool  itself  is  secreted  by  the  glands  of  the 
skin.  This  is  removed  from  the  wool  by  hot  water ;  from 
it  potassium  carbonate  and  a  valuable  oil  are  obtained. 
Some  potassium  carbonate  is  also  prepared  from  potassium 
chloride,  as  sodium  carbonate  is  made  from  the  chloride. 
Potassium  carbonate  is  a  white  crystalline  salt,  which  is 
very  deliquescent.  Commercially,  it  is  known  as  pearl 
ash.  As  already  stated,  it  is  used  in  making  Bohemian 
and  flint  glass.  From  it  also  potassium  hydroxide  is  pre- 
pared. 

23.  Potassium   Hydroxide,   KHO. — This   is   made   by 
processes  exactly  similar  to  those  for  making  sodium 
hydroxide,  thus, 

K2C03  +  Ca(HO)2  -»  2KHO  +  CaC03. 

The  calcium  carbonate  is  an  insoluble  compound  and  the 
hydroxide  may  be  decanted  or  filtered  off.  It  may  also 
be  prepared  electrolytically  from  potassium  chloride  as 
is  caustic  soda.  Commercially  it  is  known  as  caustic 
potash.  It  is  a  white  solid,  extremely  deliquescent,  and 
caustic,  similar  in  all  respects  to  caustic  soda.  It  is  used 
chiefly  in  making  soft  soap ;  a  special  variety  prepared 
for  the  drug  trade  is  made  by  combining  the  caustic 
potash  with  linseed  oil.  This  is  used  in  making  certain 
salves  and  other  pharmaceutic  preparations. 

24.  Potassium  Nitrate,  KNO:,. — This  compound  occurs 
in  limited  quantities  in  the  soil  in  certain  parts  of  Per- 
sia and  India.    It  is  supposed  to  be  formed  through  the 
action   of  bacteria   upon   animal   refuse.      Considerable 
amounts  are  made  from  Chile  saltpeter  by  treating  that 
salt   with  potassium   chloride.     Potassium  nitrate   is   a 


324  APPLIED    CHEMISTRY 

white  crystalline  salt,  not  greatly  different  from  com- 
mon salt  in  taste.  Commercially,  it  is  known  as  salt- 
peter. It  is  used  to  some  extent  in  curing  meats 
but  mainly  for  making  gunpowder.  The  composition  is 
not  materially  different  from  that  given  when  sodium 
nitrate  is  used,  75  per  cent  of  the  mixture  being  saltpeter. 
Sulphur  and  charcoal  with  a  little  moisture  make  up  the 
balance.  When  exploded,  the  gases  formed  are  mostly 
nitrogen  and  one  or  both  of  the  oxides  of  carbon.  The 
smoke  produced  when  fired  in  a  gun  is  a  mixture  of  two  or 
more  solid  compounds,  mainly  potassium  sulphide  and 
potassium  carbonate.  Partly  because  of  the  smoke  and 
partly  because  less  powerful,  ordinary  black  powder  is 
being  largely  supplanted  by  smokeless  powders  which 
have  been  mentioned  on  p.  156. 

25.  Potassium  Chlorate,  KC103. — This  salt  is  a  white 
crystalline  solid.     It  melts  easily  in  the  Bunsen  burner 
and  decomposes,  forming  potassium  chloride.     All  the 
oxygen  is  evolved,  thus, 

2KC103  -»  2KC1  +  302. 

In  the  presence  of  manganese  dioxide,  which  serves  as 
a  catalytic  agent,  when  heated  the  decomposition  is 
rapid.  Potassium  chlorate  is  used  in  the  preparation  of 
oxygen,  in  making  fireworks,  and  in  matches,  as  already 
described.  It  has  a  mild,  cooling  taste,  and  is  sometimes 
used  to  allay  irritation  of  the  throat  and  coughing. 

26.  Other  Compounds. — Potassium  bromide  and  iodide 
are  white  compounds  which  crystallize  in  cubes  consid- 
erably larger  than  those  of  common  salt.    They  are  both 
very  soluble  in  water,  and  are  both  used  to  some  extent 
in  medicine.     The  former  is  a  sedative  and  the  latter 
an  alterative.     Potassium  bromide  is  also  used  in  pho- 
tography as  a  means  of  preparing  the  silver  bromide 


THE   ALKALI    METALS  325 

upon  the  plates  and  films.  Potassium  cyanide,  KCN, 
is  a  white  compound,  very  deliquescent,  with  a  peculiar, 
unpleasant  odor.  It  is  one  of  the  most  violent  poisons 
known.  Its  chief  use  is  in  silver  and  gold  plating  and 
as  a  means  of  extracting  gold  from  its  ores  by  what  is 
known  as  the  cyanide  process. 

Exercises  for  Review 

1.  Name  the  metals  of  the  sodium  group.     By  what  other  name 
are  they  known?     Why  s:>  called? 

2.  Give  in  some  detail  the  occurrence  of  common  salt  upon  the 
earth. 

3.  Who  discovered  sodium?     How  is  it  prepared  now? 

4.  Describe   sodium.     How   is   it   preserved?     Why? 

5.  What  is  an  amalgam?   What  use  is  made  of  sodium  amalgam? 

6.  Give  methods  of  preparing  common  salt  for  the  market. 

7.  Give  the  chief  properties  of  common  salt. 

8.  What  causes  table   salt  to  become   damp?     How  is  this  pre- 
vented in  some  samples? 

9.  Give  uses  for  common  salt.     State  amount  used  per  capita. 

10.  WThat  is  sodium  bicarbonate?     How  did  it  receive  the  name? 
How  is  it  prepared  now? 

11.  How  is  sodium  carbonate  made?     Give  steps  in  the  Leblanc 
process  and  write  the  equations,  omitting  the  coke  from  your  last 
equation. 

12.  Give  some  important  uses  for  sodium  carbonate. 

13.  What  is  sal  soda?     Why  does  it  give  an  alkaline  reaction  in 
water  ? 

14.  What  is  hydrolysis?     State  what  kind  of  a  litmus  reaction  a 
solution  of  each  of  the  following  will  give :    sodium  nitrate,  potas- 
sium sulphate,  copper  chloride,  potassium  carbonate,  aluminum  sul- 
phate, potassium  chloride,  ammonium  nitrate. 

15.  Describe  the  reason  for  each  case  of  the  above. 

16.  Describe  caustic  soda  and  give  uses. 

17.  How  is  soap  made?     What  by-product  is  obtained?     How  is 
it  separated? 

18.  How  can  you  determine  whether  a  soap  contains  free  alkali? 
Why  will  all  soaps  dissolved  in  water  give  an  alkali  test? 


326  APPLIED    CHEMISTRY 

19.  Give  the  chemical  names  for  borax,  caustic  soda,  Chili  salt- 
peter, pearl  ash,  baking  soda,  sal  soda,  caustic  potash,  saltpeter. 

20.  Give  some  uses  for  borax.     Explain  what  it  does  as  a  flux  in 
soldering. 

21.  Describe  potassium  and  compare  with  sodium. 

22.  What    is    the    origin    of    the    word    potassium?      Give    three 
sources  of  potassium  carbonate.     What  uses  has  it? 

23.  What  is  saltpeter  used  for?     Wliat  is  produced  when  gun- 
powder is  exploded? 

24.  Why    are    smokeless    powders    supplanting    ordinary    black 
powder? 

25.  Describe  potassium  chlorate  and  give  uses.     What  is  its  pur- 
pose in  a  match  head? 

26.  What  use  has  potassium  cyanide? 

27.  Give  formulas  for  sal  soda,  anhydrous  sodium  carbonate,  po- 
tassium chlorate,  borax,  caustic  soda,  pearl  ash. 

28.  Complete  the  following  equations  and  state  \\liat  they  indi- 
cate: 

Na2CO3  +  Ca(HO)2  -»  , 
KC1O3  heated  -»  , 
Na  +  H20  ->  , 
H2SO4 -i- NajCl  ->  , 
NaHCO3  (heated)   ->  , 
K2C08  +  H20  -»  . 

Note. — In  completing  these  equations,  the  student  may  use  any 
quantity  needed. 


CHAPTER  XXVI 

SOME  LEAVENING  AGENTS 
Outline — 

Chemical  Agents 

(«)   Baking  Soda 

(&)   Baking  Powders 

(c)   Comparative   Healthfulness 
Yeast  as  a  Leavening  Agent 
Salt-rising  Bread 
Aerated  Bread 
Beaten  Biscuits 

1.  Baking  Soda. — The  most  common  chemical  reagent 
used  in  leavening  bread  is  sodium  bicarbonate,  sold 
as  soda  or  bakiny  soda.  It  has  been  in  use  for  years. 
The  flour  with  the  soda  well-mixed  is  "wet  up"  with 
sour  milk  or  buttermilk  both  of  which  contain  lactic 
acid.  The  acid  reacting  with  the  soda,  forms  carbon 
dioxide  as  shown  by  the  following  equation, 

NaHC03  +  HC3II,O3  -*  C02  +  H20  +  NaC3H503- 

The  carbon  dioxide,  formed  throughout  the  dough,  when 
greatly  expanded  by  the  heat  of  the  oven,  tends  to  escape. 
In  most  flours  there  is  a  considerable  amount  of  a  com- 
pound called  "gluten"  through  which  the  gas  cannot 
readily  pass :  in  its  effort,  however,  the  dough  is  raised 
and  the  bread  is  made  light  and  porous.  This  gluten 
may  be  obtained  for  examination  by  tying  a  spoonful 
of  flour  in  a  thin  cloth  and  washing  for  sometime  in. 
cold  water.  The  starch  granules  will  pass  through  the 
cloth  and  disappear  in  the  water.  A  sticky,  gummy  mass, 
which  is  mainly  gluten,  will  be  left  behind.  It  is  a  nitrog- 
enous compound  and  is  the  muscle  building  part  of  the 
flour. 

327 


328  APPLIED    CHEMISTRY 

There  is  one  difficulty  in  the  way  of  successful  use  of 
soda  as  a  leavening  agent.  It  has  been  explained  else- 
where, that  it  is  the  lactose,  or  milk  sugar,  that  by  fer- 
mentation produces  the  lactic  acid  in  sour  milk.  When 
the  milk  first  begins  to  taste  sour  the  quantity  of  acid 
present  is  not  large,  but  continually  increases  until  all 
the  lactose  has  been  changed.  It  is  impossible  to  know 
without  chemical  test  how  much  soda  is  needed  to  neutral- 
ize the  acid  present.  Hence,  too  little  may  result  in  a 
sour  and  heavy  bread,  or  too  much  may  produce  a  dis- 
colored, alkaline-tasting  bread.  In  very  warm  weather 
the  decomposition  of  milk  is  rapid ;  as  it  is  an  excellent 
medium  of  growth  for  all  kinds  of  bacteria  other  prod- 
ucts besides  lactic  acid  form,  which  may  result  in  an 
unwholesome  bread. 

2.  Baking  Powders. — The  uncertainty  of  the  results  to 
be  expected  from  the  use  of  soda  with  sour  milk  led 
to  the  preparation  of  baking  powders.  There  are  a  great 
variety  of  them  at  present,  but  the  underlying  principle 
in  all  of  them  is  the  same.  This  is  the  formation  of 
carbon  dioxide  from  soda  by  the  use  of  an  acid  salt 
or  its  equivalent.  They  all,  therefore,  contain  sodium 
bicarbonate.  In  addition,  one  class,  known  as  the  tar- 
trate  powders,  uses  potassium  acid  tartrate,  commercially 
called  "cream  of  tartar."  A  second  class,  the  phosphate 
powders,  uses  acid  calcium  phosphate;  a  third,  usually 
called  alum  powders,  uses  aluminum  sulphate.  Besides 
these  three  classes  there  are  many  mixed  powders,  which 
usually  contain  mixtures  of  the  second  and  third.  In  all 
cases  starch  or  flour  is  added  to  the  other  ingredients 
to  prevent  chemical  action  taking  place  through  exposure 
to  the  moisture  of  the  air.  The  principle  is  the  same  as 
that  employed  in  preventing  common  salt  from  becoming 
damp  in  wet  weather. 


SOME    LEAVENING    AGENTS  329 

3.  The  Chemical  Action. — In  the  tartrate  powders  the 
reaction  is  shown  by  the  equation, 

NaIIC03  +  KHC4H40(i  -»  KNaC4H40G  +  H20  +  C02. 
It  Avill  be  seen  that  the  residue  left  in  the  baked  prod- 
uct   is    potassium    sodium    tartrate,    known    as    Rochelle 
salt.     When  phosphate  powders  are  used  the  following 
reaction  takes  place, 

4XaHCO,  +  CaH4(P04),   -»   CaNa4(P04)2 +  4H20  +  4C02. 

As  will  be  seen,  in  this  case  a  phosphate  of  sodium  and 
calcium  is  left  in  the  bread  or  cake,  a  compound  not 
greatly  different  from  the  phosphate  contained  in  the 
bones.  With  the  alum  powders  the  reaction  is  somewhat 
more  complicated.  Aluminum  sulphate  is  not  an  acid 
salt  and  its  action  depends  upon  the  complete  hydrolysis 
of  the  aluminum  carbonate  and  the  instability  of  the 
carbonic  acid  formed.  This  will  be  made  clearer  by 
observing  the  equations  below, 

Al2(SOJ3  +  6NaHC03  -> 

3Na2S04  +  A12  (C03)  3  +  3H20  +  3C02. 

This  shows  the  results  of  the  interaction  of  the  two 
salts  when  brought  together  by  the  milk  or  water  used 
in  the  dough.  But  it  will  be  remembered  that  salts 
formed  from  weak  acids  with  weak  bases  are  completely 
hydrolyzed  in  water.  Aluminum  carbonate  is  such  a 
compound.  Hence,  immediately  a  second  reaction  be- 
gins, thus, 

A12(C03)3  +  6HOH  ->  A12(HO)6  +  3C02  +  3H20. 
It  will  be  seen  from  the  equations  that  the  carbon  di- 
oxide is  evolved  in  two  successive  steps.  In  most  of 
the  alum  powders,  the  soda  is  in  such  proportion  as  to 
furnish  only  about  two-thirds  as  much  available  carbon 
dioxide  as  that  given  by  the  other  powders;  but  to  offset 


330  APPLIED    CHEMISTRY 

this,  the  manufacturers  claim  that  the  evolution  of  the 
gas,  in  stages  and  not  all  at  once,  more  than  compen- 
sates for  the  smaller  amount  produced,  in  that  the  loss  is 
much  less  in  making  up  and  handling  the  dough.  It  will 
be  noticed  that  the  two  products  which  remain  in  the 
bread  in  this  case  are  sodium  sulphate  and  aluminum 
hydroxide.  It  must  be  remembered  that  baking  powders 
are  not  used  with  sour  milk,  for  the  acid  salt  or  the 
alum  takes  the  place  of  the  lactic  acid  and  the  different 
ingredients  are  so  proportioned  that  at  the  close  of 
the  operation  there  shall  be  no  excess  of  either.  One 
or  more  well-known  brands  of  baking  powders  incor- 
porate with  the  other  ingredients  a  small  quantity  of  egg 
albumin.  The  claim  of  the  manufacturers  is  that  this  in- 
creases the  viscosity  of  the  liquids  used  in  making  up 
the  dough  so  that  as  a  result  the  carbon  dioxide  will  be 
retained  the  better.  Carried  out  as  an  experiment  in  a 
test  tube  with  water  to  bring  about  the  reaction  and 
no  flour  present,  this  is  found  to  be  true.  But  in  the 
biscuit,  itself,  the  claim  is  a  very  doubtful  one.  Sugges- 
tions have  been  made  to  use  hydrochloric  acid  with 
soda  as  a  leavening  agent.  Its  reaction  is 

NaHC03  +  HCl  -»  Nad  +  H20  +  C02. 

It  shows  that  only  common  salt  is  left  in  the  bread.  The 
objection  to  this  is  that  the  hydrochloric  acid  is  a  liquid 
and  therefore  cannot  be  mixed  with  the  soda  before- 
hand. Each  separate  portion  would  have  to  be  meas- 
ured out  at  the  time  of  using,  so  that  the  inconvenience 
might  outweigh  other  considerations.  The  salt  formed 
in  a  given  quantity  of  bread  is  only  about  half  what  is 
ordinarily  mixed  with  the  flour;  hence  no  objection 
could  be  offered  in  that  respect.  Scores  of  actual  ex- 
periments with  muffins,  biscuits,  every  variety  of  cake 
and  doughnuts,  have  been  carried  out  by  the  author's 


SOME    LEAVENING    AGENTS  331 

students   using1  soda   and  hydrochloric   acid,   with   uni- 
formly successful  results. 

4.  Healthfulness  of  Baking  Powders. — Owing  to  the 
intense  rivalry  among  the  manufacturers  themselves,  the 
public  has  taken  more  or  less  interest  in  the  comparative 
healthfulness   of   the   various    baking   powders    on   the 
market.    A  general  idea  prevails  that  the  tartrate  pow- 
ders are  the  most  wholesome ;  this  has  come  through  un- 
limited advertising  by  the  manufacturers  of  that  class 
of  powders.    Food  experts  of  the  United  States  who  have 
given  special   attention  to   the  effects   of  adulterations 
and  preservatives  in  foods  unite  in  saying  that  all  bak- 
ing powders  leave  in  the  bread  one  or  more  substances 
classed  as  drugs,  and  since  no  efforts  have  ever  been  made 
to  ascertain  the  effects  in  small  quantities  of  these  sub- 
stances upon  the  human  system,  no  one  can  say  what  the 
result  is  upon  health.     Inasmuch  as  the  quantity  con- 
sumed by  any  individual  is  not  great,  it  is  probable  that 
the  effects  upon  health  are  so  small  as  to  be  negligible  in 
the  case  of  any  of  the  powders.     Moreover,  other  kinds 
of  bread  in  which  baking  powders  are  not  used  seem  to 
be  gaining  in  use  and  popularity  in  America;  hence,  the 
discussion  may  well  be  left  until  it  has  been  settled  by 
actual  experiment. 

5.  Yeast  Bread. — A  very  considerable  amount  of  the 
bread  used  at  the  present  time,  especially  in  cities,  is 
what  is  commonly  called  "light  bread"  or  that  in  which 
yeast  is  the  leavening  agent.     Yeast  is  a   microscopic 
plant  which  grows  rapidly  in  a  mixture  of  flour  and 
water,   if   kept   warm.      As    the    growth   proceeds,    the 
sugar  added  and  the  starch  which  is  changed  into  invert 
sujrar  as  explained  elsewhere,  p.  220,  are  transformed 
into  alcohol  and  carbon  dioxide  thus, 

C(;H120(;  -»  2aiI5OH  +  2CO,. 


332  APPLIED    CHEMISTRY 

The  equation  showing  the  inversion  of  the  starch  is 
C6H1005  +  H20  -*C6H1206- 

When  the  dough  has  risen  to  a  certain  extent  it  is 
kneaded  back;  this  breaks  up  the  bubbles  of  gas  into 
a  very  large  number  of  small  ones  and  gives  a  loaf 
of  much  more  uniform  texture.  When  heated  in  the 
oven  the  alcohol  is  expelled,  since  its  boiling  point  is 
only  78°.  The  carbon  dioxide  is  expanded  so  as  to 
raise  the  dough  and  the  yeast  plants  are  killed.  From 
the  fact  that  large  bakeries  can  control  and  maintain 
uniform  conditions  of  temperature  in  their  establish- 
ments, and  more  than  this,  can  secure  uniform  quality  of 
flour  by  blending  if  necessary,  their  product  is  fast 
supplanting  that  made  in  the  home.  It  has  been  said 
before  that  it  is  the  gluten  that  serves  to  hold  the  gas 
in  the  dough  until  the  baking  is  completed.  Naturally, 
therefore,  a  flour  deficient  in  this  respect  will  not  rise 
well;  one  with  too  much  will  produce  bread  too  light, 
with  large  pores.  For  this  reason,  up  to  within  recent 
years,  it  was  difficult  for  the  housewife  with  different 
flours  to  make  a  uniformly  satisfactory  loaf,  yet  with 
no  fault  on  her  part.  At  present,  all  large  flour  mills 
have  the  wheat  they  intend  buying  tested  as  to  per- 
centage of  gluten  as  well  as  in  other  respects.  The 
flours  they  make  are  likewise  tested.  Thus  with  the 
composition  known,  a  flour  low  in  gluten  may  be  mixed 
with  one  having  a  high  percentage  and  both  will  be 
made  right.  At  the  present  time,  the  output  of  flour 
is  much  more  uniform  than  some  years  ago.  This  has 
resulted  in  large  baking  concerns  themselves  putting 
out  a  much  more  uniform  product  than  was  possible 
formerly.  Since  carbon  dioxide  in  yeast  bread  is  ob- 
tained through  the  decomposition  of  the  starch,  it  will 


SOME    LEAVENING    AGENTS  333 

be  seen  that  there  must  be  considerable  loss  in  weight. 
In  baking,  including  the  Avater,  which  escapes,  this  is 
fully  15  or  20  per  cent.  It  was  estimated  by  Liebig,  a 
German  chemist,  some  years  ago,  that  the  alcohol  pro- 
duced in  this  way  amounted  in  the  German  empire  to 
twelve  million  gallons  annually,  and  that  the  flour  thus 
passing  off  into  the  air  in  gaseous  form  was  sufficient 
for  the  bread  required  by  an  army  of  30,000  men. 

Formerly  the  housewife  was  dependent  largely  upon 
her  own  efforts  for  a  continued  supply  of  yeast.  A 
piece  of  dough  was  saved  each  time  and  put  away  in 
a  cool  place  until  time  for  the  next  baking.  Sometimes 
this  was  mixed  with  corn  meal  and  dried,  in  which  case 
it  was  good  for  several  weeks  or  even  longer.  Later 
dry  yeast  was  made  an  article  of  commerce  and  sold 
under  the  trade  name  of  "Yeast  Foam."  At  the  present 
time  "compressed  yeast"  which  is  a  fresh  and  not  a 
dried  yeast  has  largely  supplanted  the  dry  form  because 
of  its  very  much  more  rapid  growth  when  put  into 
"sponge."  Large  bakeries  use  a  yeast  in  a  semi-liquid 
condition  closely  resembling  thin  batter. 

6.  Salt  Rising  Bread. — This  special  variety  is  made  by 
mixing  up  a  sponge  of  corn  meal,  and  milk  with  some 
salt  added,  and  allowing  it  to  stand  for  some  hours. 
Thereafter  the  procedure  is  not  essentially  different 
from  that  of  ordinary  bread.  It  is  supposed  that  a 
special  variety  of  yeast  spore  which  grows  rapidly  in 
the  corn  meal  mixture  and  which  finds  entrance  from 
the  air  is  the  cause  of  the  leavening  and  of  the  pecu- 
liar taste  as  well.  Some  few  years  ago  this  "wild 
yeast"  was  isolated  by  a  graduate  student  at  Kansas 
University,  and  salt  rising  bread  may  now  be  made 
with  as  much  assurance  of  uniform  results  as  with  or- 
dinary yeast. 


334  APPLIED   CHEMISTRY 

7.  Aerated  Bread. — On  account  of  the  loss  in  weight 
in  light   bread  as   explained   above,   efforts   have   been 
made  to  force  carbon  dioxide  into  the  dough  mechani- 
cally, without  the  use  of  any  yeast  at  all.     This  is  done 
by  putting  the  materials  into  large  cylinders  and  pump- 
ing in  carbon  dioxide  until  a  considerable  pressure  is 
reached.     It  is  then  kneaded  mechanically  by  rotating 
the  cylinders.    After  some  time  the  dough  is  forced  out, 
cut  into  suitable  sizes  and  baked.     The  gas  absorbed, 
having    the    pressure    removed    and    the    temperature 
greatly  raised,  expands  in  accordance  with  both  Boyle's 
and  Charles'  laws  and  makes  the  product  porous  and 
light.    The  bread  thus  obtained  is  sweet  and  wholesome, 
but  lacks  the  "yeasty"  taste;  it  is  more  inclined  to  be 
dry  than  ordinary  bread  and  has  not  been  received  well 
by  the  public. 

8.  Beaten  Biscuits. — These  were  probably  the  original 
aerated  bread.    No  leavening  agent  is  used,  but  by  con- 
tinued  kneading   and   "beating"   more    or   less   air   is 
worked  into   the  dough,  which   expands  upon  baking. 
Such  biscuits  are  never  as  light  as  those  made  from  soda 
or    baking   powder,    but   they   retain   all    the   relative, 
wholesome  taste  of  the  flour,  with  nothing  objectionable 
or  questionable  added.     The  amount  of  time  needed  to 
make  them  is  fast  causing  them  to  be  an  unknown  ar- 
ticle of  food. 

Exercises  for  Review 

1.  Explain  the   action   of    soda   in  making   biscuits.     Write   the 
equation. 

2.  What   prevents   a   gas   escaping    rapidly   from   'dough?      How 
may  a  sample  be  obtained  for  examination? 

3.  What    difficulty    is   there    in    obtaining   uniform    results    with 
soda  ? 

4.  Name  the  three  classes  of  baking  powders  and  give  compo- 
sition.     What    is   the    purpose    of    each   ingredient    in    the    baking 
powders  ? 


SOME   LEAVENING   AGENTS  335 

5.  What  is  left  in  the  bread  in  the  case  of  each  baking  powder? 

6.  Why  can  biscuit  made  from  a  baking  powder  never  shoAv  an 
alkaline  reaction? 

7.  Give  advantages  and  disadvantages  of  using  hydrochloric  acid 
with  soda  as  a  leavening  agent. 

8.  What  may  be  said  of  the  relative  healthfulness  of  the  various 
baking  powders? 

9.  What  is  yeast?     How  does  it  leaven  bread?     Why  were  light 
breads  in  former  years  of  such  varying  quality?     Why  more  uni- 
form now? 

10.  What  can  be  said  of  the  loss  in  making  yeast  bread? 

11.  What  is  aerated  bread?     How  is  the  gas  introduced  into  the 
dough?    What  advantages  has  it?    Why  has  it  not  become  popular? 

12.  How  are  beaten  biscuits  made?     What  disadvantage  regard- 
ing them? 


CHAPTER  XXVII 

THE  CALCIUM  FAMILY 

Outline- 
Members  of  the  Group 
Occurrence  of  Calcium 
Properties  of  Calcium 
Lime 

(a)   Manufacture 

(&)  Uses 
Plaster  of  Paris 
Cements 

(a)   Natural  and  Portland 

(6)   Concrete  Work 
Chalk 

Calcium  Chloride 
Strontium  and  Barium 

1.  Metals  of  the  Group. — The  metals  belonging  to  this 
group  are  calcium,  strontium,  barium  and  radium,  rang- 
ing in  atomic  weights  from  40  to  226.     The  first  three 
react  with  cold  water  and  form  hydroxides,  which  are 
strongly  alkaline  although  not  very  soluble.     They  are 
often  called  the  alkaline  earth  metals. 

2.  Occurrence  of  Calcium. — Rocks  containing  calcium 
compounds  are  among  the  most  abundant  of  the  earth's 
crust.     Limestone  and  the  semicrystalline  variety,  mar- 
ble, are  both  calcium  carbonate  as  are  also  corals  and 
shells.    Limestone  is  produced  by  the  cementing  together 
of  shells  and  similar  material  ground  up  by  the  action 
of   the    waves.     Fossil   remains    of   crinoid    stems   and 
brachiopods  are  commonly  seen  in  ordinary  limestone. 
The  famous  coquina  rock,  from  which  the  old  Spanish 
fort  at  St.  Augustine  in  Florida  was  built,  is  made  en- 

336 


THE    CALCIUM  FAMILY  337 

tirely  of  coarse  fragments  of  shells,  firmly  cemented  to- 
gether. Marble  is  usually  more  free  from  silica  and  other 
impurities  than  common  limestone.  It  has  been  subjected 
to  intense  heat  at  some  time  in  the  earth's  history  such 
that  it  was  softened  and  upon  cooling  became  more  or 
less  crystalline  in  structure.  Chalk  beds  are  composed  of 
the  remains  of  the  shells  of  microscopic  animals,  known 
as  globigerina.  In  some  parts  of  the  ocean  at  the  present 
time  globigerina  ooze  is  being  deposited  where  chalk 
beds  of  a  future  day  may  be  found.  Calcium  carbonate 
also  occurs  in  crystals,  often  of  considerable  size,  in  the 
shape  of  flat  rhombohedrons  and  sometimes  in  six-sided 
crystals,  known  as  "dog-tooth  spar."  It  is  sometimes 
mistaken  for  quartz,  but  need  not  be,  for  its  hardness 
is  only  three  in  the  scale  while  that  of  quartz  is  seven. 
Gypsum,  calcium  sulphate,  is  also  widely  distributed.  One 
very  pure  variety,  known  as  alabastine,  is  often  beauti- 
fully colored  and  is  used  for  vases  and  similar  wares. 
The  native  phosphate  of  calcium  as  well  as  feldspars  con- 
taining calcium  have  been  mentioned  elsewhere. 

3.  Description   of   Calcium.— It    has   not   been   many 
years  since  calcium  became  an  article  of  commerce,  but 
it  was  first  prepared  more  than  a  century  ago  by  Sir 
Humphrey  Davy,  by  methods  similar  to  those  he  used 
for  sodium  and  potassium.     It  is  now  made  by  electro- 
lyzing  melted  calcium  chloride,  much  as  sodium  is  by 
the  Castner  process.    It  is  a  silvery  white  metal,  resem- 
bling sodium,   but  much   harder.     It   may   be   cut   and 
worked  much  as  lead  may  be.     It  reacts  readily  with 
water  Avith  the  evolution  of  hydrogen;  when  heated  it 
combines  rapidly  with  chlorine,  bromine  and  oxygen. 

4.  Lime,  CaO. — This  compound  is  made  by  calcining 
limestone  in  kilns.     The  native  rock  is  heated  strongly 


338  APPLIED    CHEMISTRY 

with  coke  or  wood  for  several  clays  during  which  the 
carbon  dioxide  is  expelled,  thus, 

CaC03  -»  CaO  +  C02. 

The  better  lime  kilns  are  arranged  so  that  the  process 
is  continuous.  Limestone  is  fed  in  from  above,  while 
the  finished  product  may  be  removed  at  the  bottom.  It 
is  then  shipped  in  barrels  or  loose  to  points  where 
needed.  Exposed  to  the  air  lime  absorbs  moisture  and 
carbon  dioxide  and  crumbles  to  a  fine  powder.  Ulti- 
mately it  becomes  a  carbonate  again,  so  that  the  above 
reaction  might  be  written 

CaC03  ?±  CaO  +  C02. 

It  reacts  with  water  vigorously  with  the  evolution  of 
much  heat.  Use  is  made  of  this  fact  by  balloonists  as 
a  means  of  securing  heat  at  high  altitudes  without  the 
use  of  fire.  In  case  of  considerable  quantities  of  lime 
in  contact  with  wood  or  other  combustible  material,  the 
temperature  reached,  on  the  addition  of  water,  is  often 
sufficient  to  cause  combustion.  An  illustration  of  this 
was  seen  at  the  time  of  the  flood  of  the  Kansas  River  at 
Kansas  City  in  1903,  when  many  box  cars  loaded  with 
lime  were  partially  submerged  in  the  freight  yards. 
All  of  them  took  fire  and  burned  to  the  surface  of  the 
water. 

5.  Uses  of  Lime. — One  of  the  most  important  uses  is 
for  making  mortar  in  building— foundations  for  houses, 
brick  work,  stone  walls,  and  the  like.  For  large  build- 
ings, cement  is  used  because  of  its  greater  strength,  but 
it  will  be  seen  later  that  cement  contains  a  considerable 
percentage  of  lime.  Mortar  is  made  by  mixing  sand 
with  slaked  lime.  When  exposed  to  the  air,  as  in  the 
foundation  of  a  building:,  chemical  reaction  with  the 
carbon  dioxide  of  the  air  takes  place,  the  water  is  evap- 


THE    CALCIUM  FAMILY  339 

orated,  and  ultimately,  if  properly  made,  the  mortar 
becomes  a  silicious  limestone.  Thus, 

Ca(HO)2  +  C02  ->  CaC03  +  ILO. 

As  the  carbon  dioxide  in  the  air  is  limited  in  amount, 
the  action  is  slow  and  probably  continues  for  months  or 
even  longer.  Moisture  aids  in  the  absorption.  Slaked 
lime  is  often  used  to  remove  the  hair  from  hides ;  boiled 
with  sulphur  it  is  used  as  a  spray  to  prevent  fungous 
destruction  of  peaches,  plums,  grapes  and  possibly  other 
fruits,  Molded  into  round  sticks  it  is  used  in  the  cal- 
cium light,  already  mentioned  on  p.  68.  It  is  also 
valuable  as  a  whitewash  for  basements,  board  walls, 
trees  and  as  a  cheap  disinfectant.  Dilute  solutions  of 
the  hydroxide  are  called  lime  water  and  are  used  in 
various  ways  in  medicine.  Milk  of  lime,  which  is  water 
containing  considerable  calcium  hydroxide  in  suspen- 
sion is  used  with  alum  in  settling  the  mud  from  river 
water  for  city  supplies,  also  as  a  means  of  softening 
water,  which  will  be  explained  later. 

6.  Plaster  of  Paris. — tty  calcining  gypsum  at  such  a 
temperature  as  to  remove  a  portion  of  the  water  of 
combination,  plaster  of  Paris  is  obtained.  The  reaction 
is 

CaS04.2H20  -»  CaS04.H20  +  H20. 

As  put  on  the  market  it  is  a  white  powder.  Its  most  re- 
markable property  is  that  of  being  able  to  take  up  water 
and  change  back  rapidly  into  the  hydrated  form 
again.  This  property  is  called  "setting."  If  the  quan- 
tity of  water  is  not  too  great  it  takes  place  in  a  very 
short  space  of  time.  Examination  with  a  magnifying 
glass  shows  the  formation  of  a  crystalline  structure. 
In  preparing  plaster  of  Paris,  if  the  calcining  is  con- 
tinued sufficiently  long  to  expel  all  the  combined  water, 
the  product  is  called  "burnt  plaster"  and  has  very  little 


340  APPLIED    CHEMISTRY 

value,  for  it  takes  up  water  again  very  slowly.  Plaster 
of  Paris  is  used  in  the  finishing  coat  in  plastering  houses, 
for  making  plaster  casts  and  statuary,  in  dental  and 
other  surgery,  for  interior  raised  decorations  in  large 
halls,  panel  work,  as  a  filler  for  paper  pulp,  for  school 
crayons,  and  in  numerous  other  ways.  When  used  in 
statuary,  to  prevent  injury  in  washing,  since  calcium  sul- 
phate is  somewhat  soluble  in  water,  the  surface  is 
usually  treated  with  a  solution  of  paraffin  in  naphtha  or 
some  similar  volatile  oil.  Gypsum  is  often  called  "land 
plaster"  and  is  frequently  used  as  a  corrective  of  alka- 
linity in  soils. 

7.  Cements. — This  class  of  complex  substances  may  be 
divided  into  natural  and  portland  cements.  They  all 
contain  more  or  less  lime,  usually  some  magnesia,  MgO, 
with  silica,  and  aluminum  oxide  as  the  main  ingredients. 
The  first  two  of  these  are  usually  found  together  in 
what  is  called  magnesium  limestone;  the  others  are  ob- 
tained from  shale,  a  hydrated  aluminum  silicate.  When  a 
quarry  of  rock  contains  all  of  these  in  such  proportions 
as  are  more  or  less  suited  for  the  manufacture,  the  cement 
made  therefrom  is  called  a  natural  cement.  However 
when  the  limestone  is  obtained  from  one  quarry  and  the 
other  rock  from  another,  it  is  called  a  portland  cement. 
This  last  name  was  given  in  England  for  the  reason  that 
when  used  the  finished  product  resembled  closely  a  spe- 
cial building  stone  known  as  Portland  rock.  Natural  ce- 
ments, as  a  rule,  are  comparatively  high  in  the  lime  con- 
tent. As  this  sets  by  the  absorption  of  carbon  dioxide 
from  the  air,  such  cements  harden  slowly.  In  preparing 
portland  cement  the  separate  portions  are  weighed  in 
such  amounts  as  have  been  found  by  experience  to  be 
best,  are  then  calcined,  mixed  and  ground  to  a  fine  pow- 
der. In  the  calcining  two  changes  take  place :  the  carbon 


THE    CALCIUM   FAMILY  341 

dioxide  is  expelled  from  the  limestone  and  a  part  of  the 
water  from  the  hydrated  shale.  These  steps,  in  a  sim- 
ple way,  may  be  illustrated  thus, 

CaMg(C03),  -*  CaO  +  MgO  +  2C02, 

Al4(Si04)aiiH20  ->  Al4(SiOJ3mH20  +  xH20. 

As  plaster  of  Paris  sets  quickly  through  the  hydration  of 
the  molecules,  so  any  cement  with  the  partially  dehy- 
drated silicate  in  excess  will  also.  Since  this  is  true  of 
all  portland  cements,  they  harden  rapidly  even  in  the 
presence  of  much  moisture  and  are  for  this  reason  often 
called  hydraulic  cements.  For  work  in  very  cold  weather 
cements  with  very  high  content  of  silicate  are  sometimes 
used;  hence,  they  set  before  they  have  time  to  freeze. 
On  the  other  hand,  natural  cements  cannot  be  used  under 
any  such  conditions  or  where  much  moisture  will  be  pres- 
ent, as  in  piers  for  bridges,  sewers,  and  similar  places, 
for  they  set  too  slowly.  Likewise,  they  cannot  be  used  in 
large  buildings,  for  the  weight  to  which  they  are  subjected 
before  thoroughly  hardened  is  sufficient  to  crush  them. 

Concrete  is  made  by  mixing  cement,  sand  and  crushed 
rock,  often  called  "grits,"  in  the  proportion  of  1,  3,  and  5. 
Water  is  added  and  the  whole  rotated  in  a  mechanical 
mixer  till  relatively  homogeneous.  This  is  then  poured 
into  position  and  allowed  to  harden.  Thus  are  made 
roadways,  sidewalks,  foundations,  bridge  piers,  and  a 
vast  number  of  other  things.  Much  of  the  building  in 
cities  now  is  of  reenforced  concrete.  This  is  made  by 
putting  iron  rods  into  position  and  pouring  the  concrete 
mixture  over  and  about  them.  For  roadways,  woven  wire 
fencing  is  sometimes  used.  Floors  of  fireproof  buildings 
and  roofs,  supported  temporarily  by  false  woodwork  are 
thus  made.  The  reenforcement  enables  the  concrete  to 
withstand  any  sudden  shocks  or  great  strain.  The  great 


342  APPLIED    CHEMISTRY 

earthquake  and  fire  resulting  in  San  Francisco  in  the 
spring  of  1906  gave  great  impetus  to  this  method  of  build- 
ing. It  was  found  that  the  reenforced,  fireproof  con- 
struction was  able  to  stand  with  relatively  little  damage 
even  such  terrible  forces  of  destruction.  During  the  last 
year  of  the  Great  War  reenforced  concrete  was  even  used 
for  a  number  of  medium-sized  ocean  going  vessels.  Its 
uses  are  being  extended  more  and  more  every  year,  since 
lumber  is  becoming  more  scarce.  In  1915,  government 
bulletins  showed  that  there  was  an  output  in  the  United 
States  of  90,000,000  barrels  of  cement,  with  great  in- 
creases each  year  over  the  preceding.  During  the  war 
this  fell  off  some,  because  little  building  was  done,  but 
only  temporarily. 

8.  Prepared  Chalk. — Native  chalk,  it  has  been  said,  is 
formed  from  the  minute  shells  of  sea  animals  cemented 
together.     It  may  be  prepared  artificially  by  treating 
a  solution  of  some  calcium  compound  with  sodium  car- 
bonate in  solution,  thus, 

CaCl2  +  Na2C03  -»  CaC03  +  2NaCl. 

The  carbonate  is  a  white  precipitate;  it  is  filtered  out, 
washed,  and  molded  into  the  desired  shape  or  used  as  a 
powder.  Properly  made  it  is  a  perfectly  smooth  powder, 
entirely  free  from  any  gritty  feeling.  It  is  used  in 
tooth  powders  and  pastes,  as  well  as  in  a  variety  of 
other  ways  in  pharmacy. 

9.  Calcium    Chloride,    CaCl2, — This    compound    is    a 
white  solid  obtained  as  a  by-product  in  the  Solvay  proc- 
ess  of   making   sodium   carbonate   and   in   some    other 
manufactures.     For  example, 

2NH4Cl  +  CaO  ->  2NH3  +  H20  +  CaCl2. 

By  evaporation  of  the  solution  thus  obtained,  the  salt 
crystallizes  out  as  a  decahydrate,  CaCl2  +  10H20,  which 


THE    CALCIUM   FAMILY  343 

is  very  soluble  in  water  and  hence  very  deliquescent. 
If  heated  strongly  the  hydrate  loses  all  its  water  and 
becomes  a  dry,  porous  solid.  It  is  this  form  which  is 
most  desirable  for  drying  gases  in  the  laboratory.  A  few 
cannot  be  dried  this  way,  as  they  form  molecular  com- 
pounds resembling  hydrates.  For  example,  ammonia 
unites  with  the  calcium  chloride,  eight  molecules  for 
one  and  forms  a  compound  with  the  formula,  CaCl2  + 
8XII3.  The  crystalline  variety  is  used  in  the  brine 
tanks  of  many  refrigerating  plants  instead  of  common 
salt.  It  is  said  to  attack  the  metal  pipes  and  boxes  less 
than  the  sodium  chloride  does.  Since  a  solution  of  cal- 
cium chloride  may  be  made  that  will  not  freeze  except 
at  very  low  temperatures  it  has  the  advantage  of  being 
able  to  be  transmitted  considerable  distances  in  re- 
frigeration systems  and  still  possess  such  a  degree  of 
cold  as  may  be  necessary.  Since  the  supply  of  calcium 
chloride  is  greater  than  the  demand,  attempts  have 
been  made  to  find  other  uses  for  it.  For  preventing 
dust  on  roadways  its  use  has  been  mentioned  on  p.  143. 
In  many  localities  asphaltic  petroleum  is  used.  This 
prevents  erosion  by  heavy  rains,  as  well  as  by  winds  and 
heavy  traffic.  The  calcium  chloride  cannot  prevent  dam- 
age by  rains  on  account  of  its  great  solubility. 

10.  Other  Members  of  the  Group. — Strontium  and  ba- 
rium occur  in  native  compounds  corresponding  to  those 
of  calcium,  the  sulphate  and  carbonate.  Barium  sul- 
phate, especially  that  made  artificially,  is  used  in  many 
ways  for  adding  weight.  Paper  pulp  intended  for  card- 
board and  white  paints  often  contain  it  as  a  filler,  or 
adulterant. 

The  nitrates  are  both  used  in  making  fireworks  and 
colored  fires.  Fusees,  used  upon  railways  to  give  warn- 
ing of  the  nearness  of  another  train,  contain  mixtures  of 
strontium  nitrate,  shellac  or  sulphur  and  potassium  chlo- 


344  APPLIED    CHEMISTRY 

rate.  The  strontium  compound  gives  the  red  color,  the 
chlorate  furnishes  oxygen  for  rapid  combustion,  and  the 
remaining  portion  is  the  fuel.  Barium  nitrate  used  in  the 
same  way  gives  a  green  fire.  These  were  formerly  used 
extensively  for  stage  effects  and  still  are  where  the 
electric  spot  light  is  not  available.  If  to  be  burned 
indoors,  shellac  and  not  sulphur  should  be  used  on  ac- 
count of  the  fumes  produced. 

Strontium  hydroxide,  Sr(HO)2,  is  used  in  the  refining 
of  cane  sugar.  It  causes  the  separation  of  portions  of 
sugar  from  the  molasses  after  the  main  crystallization 
has  taken  place  which  would  not  otherwise  be  obtained. 
Barium  forms  both  a  monoxide,  BaO,  and  a  dioxide, 
Ba02.  The  latter  is  of  interest  in  that  it  may  be  used 
for  the  manufacture  of  hydrogen  peroxide,  thus, 

Ba02  +  H2S04  ->  BaS04  +  H202. 

Barium  hydroxide,  Ba(HO)2,  is  often  used  in  the  labora- 
tory as  a  reagent  instead  of  lime  water. 

Exercises  for  Review 

1.  Name  the  metals  of  the  calcium  group.     By  what  other  name 
are  they  known? 

2.  Give    some    of    the    familiar    natural    compounds    of    calcium. 
What  is  coquina?     Marble?     Chalk?     Alabastine? 

3.  How  may  calcite  be  distinguished  from  quartz  when  the  crys- 
tals resemble? 

4.  How  is  calcium  prepared?     Describe  the  metal. 

5.  How  is  lime  made?     Equation? 

6.  Give  the  characteristics  of  lime. 

7.  Give    important    uses    of    lime.      How    does    mortar    harden? 
Show  by  an  equation. 

8.  How  is  plaster  of  Paris  made?     What  is  its  most  remarkable 
property? 

9.  Give  uses  of  plaster  of  Paris.     What  is  land  plaster? 

10.  Name   the   two   classes   of   cements   and   state   how   each   is 
obtained. 


THP:  CALCIUM  FAMILY  345 

11.  What   advantage   has   portland   over   the   other?     Can   you 
think  of  any  reason  why  the  natural  might  be  preferred? 

12.  What  is  concrete?     How  does  it  harden?    What  is  reenforced 
concrete  ? 

13.  How  is  prepared  chalk  made?     Give  uses. 

14.  What   is   the   source   of   the   calcium   chloride   of   commerce? 
What  two  varieties?     Explain  the  difference  between  them. 

15.  Give  some  valuable  uses  for  calcium  chloride. 

16.  Give   some   uses   for  the   nitrates   of   strontium   and  barium. 
Why  are  they  so  used? 

17.  Name  some  other  compounds  of  barium  and  strontium  that 
are  of  some  use. 

18.  Complete  these  equations,  using  amounts  needed, 


Ba(HO)2 

SrC03  +  HN03  ->  , 

Sr(N03)2-t-NH,HO 


CHAPTER  XXVIII 

HARD  WATERS— METHODS  OF  SOFTENING 

Outline — 

Kinds  of  Hard  Waters 
Effects  of  Hard  Waters 
Treatment  for  Hardness 

(a)   In  the  Home 

(6)   For  Commercial  Enterprises 
Effects  of  Coagulants  upon  City  Supplies 
Hardness  as  Belated  to  Soap 
Method  of  Estimating  Hardness 

1.  Kinds  of  Hardness. — Any  water  containing  mineral 
matter  in  solution  which  will  cause  a  precipitate  with 
a  soap  solution  is  said  to  be  hard.  The  soap  solution 
must  be  perfectly  clear:  when  added,  the  formation  even 
of  a  slight  cloudy  appearance  shows  that  the  water  is 
distinctly  hard.  More  often  hardness  is  caused  by  the 
presence  of  calcium  or  magnesium  salts,  but  occasionally 
by  iron.  When  the  hardness  is  such  that  boiling  will  re- 
move it,  it  is  said  to  be  temporary;  otherwise  it  is  perma- 
nent hardness.  This  does  not  mean,  however,  that  there 
is  no  possible  way  of  removing  it.  Both  kinds  of  hardness 
may  be  present  and  often  are.  Temporary  hardness  is 
caused  by  the  presence  in  the  water  of  the  acid  carbonate 
of  calcium  or  magnesium,  often  called  the  bicarbonate, 
CaH2(C03)2.  When  boiled,  decomposition  takes  place, 
with  the  formation  of  the  normal  carbonate.  This  being 
insoluble  in  water  precipitates  out,  thus, 

CaC03.H2C03  -»  CaC03  +  C02  +  H2O. 

It  is  the  compound,  CaC03,  which  collects  upon  the  inside 
of  teakettles  as  a  rough  deposit,  also  in  the  hot  water  coils 

346 


HARD    WATERS METHODS    OF    SOFTENING  347 

in  furnaces  and  water  heaters,  and  in  all  steam  boilers 
which  use  hard  water.  It  is  one  of  the  greatest  annoy- 
ances with  which  the  engineer  has  to  deal  as  well  as  one 
of  great  expense.  All  sorts  of  "water  softeners"  have 
been  put  upon  the  market  under  various  names,  many 
of  them  worthless.  Fig.  62  shows  two  actual  cases  of 
sections  of  pipe  taken  from  two  manufacturing  plants, 
which  show  that  the  "boiler  scale"  as  it  is  called  had 
nearly  closed  the  pipes.  It  is  said  that  a  layer  14  inch  in 
thickness  lessens  the  heating  effect  by  half,  or  in  other 


Fig.   62. — Scale   in   iron   pipes,   from   an   actual   case. 

words  it  is  the  equivalent  of  an  iron  pipe  5  inches  in 
thickness.  In  the  cases  shown  in  Fig.  62  the  scale  was 
about  %  incn  thick.  Under  such  conditions,  in  gas  heaters 
or  furnace  coils,  in  the  home,  the  water  in  the  tank  is 
warmed  very  slowly,  while  the  iron  of  the  pipe  is  being 
rather  rapidly  burned  away.  Finally,  it  becomes  so  thin 
that  under  the  water  pressure  it  bursts,  and  must  be 
renewed. 

Permanent  hardness  is  caused  usually  by  the  presence 
of  sulphates  of  calcium  or  magnesium,  although  the  chlo- 
ride, especially  of  magnesium,  may  be  the  cause.  As  these 


348  APPLIED    CHEMISTRY 

compounds  are  not  decomposed  at  the  temperature  of 
boiling  water,  they  remain  in  solution. 

2.  Removal  of  Temporary  Hardness.— Since  temporary 
hardness  is  caused  by  the  presence  of  an  acid  salt,  it 
would  seem  that  naturally  an  alkali  would  remove  it. 
For  laundry  and  bath  purposes  at  home,  dilute  ammonia 
water  is  thus  often  employed.  The  reaction  is  shown  by 
the  equation, 

CaC03.H2C03  +  2NH4HO   ->   CaC03  +  (NH4)2C03. 

As  the  calcium  carbonate  is  not  soluble  in  water  it  set- 
tles to  the  bottom  and  leaves  the  water  soft.  The  am- 
monium carbonate,  unless  present  in  large  quantities 
has  little  effect  upon  the  soap,  hence  is  not  objection- 
able. If  much  water  is  to  be  treated,  this  method  is  too 
expensive.  Therefore,  steam  laundries,  many  of  which 
use  from  50,000  to  100,000  gallons  of  water  per  day,  and 
other  similar  establishments,  must  employ  a  cheaper 
alkali.  The  cheapest  known  is  lime  water,  and  this  is 
used.  Daily  analysis  of  the  water  is  made  so  as  to 
know  exactly  the  amount  of  hardness  present.  This  be- 
ing known,  into  large  settling  tanks,  holding  sufficient 
for  a  day's  run,  milk  of  lime  is  added  sufficient  to  com- 
bine with  the  acid  carbonate  and  convert  it  into  the 
normal  salt.  This  reaction  takes  place, 

CaC03.H2C03  +  Ca(HO)2  ->  2CaC03  +  2H20. 

The  precipitated  carbonate  settles  to  the  bottom  and  is 
then  drawn  off  to  the  sewers.  Lime  water  cannot  be 
employed  in  the  home  because  the  quantity  of  water 
used  is  relatively  small  and  any  excess  of  the  reagent 
would  leave  the  water  as  bad  or  worse  than  before. 
Many  cities,  with  river  water  more  or  less  muddy,  use 
milk  of  lime  as  already  mentioned  on  p.  45  in  removing 
the  turbidity.  Not  only  does  it  accomplish  this,  but  to 


HARD   WATERS — METHODS   OF   SOFTENING  349 

prevent  any  excess,  even  minute,  of  the  alum  or  whatever 
is  employed  as  a  coagulant,  a  very  slight  excess  of  lime 
is  used.  This  reacts,  as  shown  above,  with  the  precipi- 
tation at  least  of  a  portion  of  the  temporary  hardness. 
In  such  treatment  of  water,  however,  for  turbidity,  the 
permanent  hardness  is  always  increased  as  the  equation 
will  show, 

Al2(S04)3  +  3Ca(HO)2  ->  3CaS04  +  A12(HO)0. 

The  aluminum  hydroxide  is  the  gelatinous  coagulum 
which  drags  down  the  mud,  but  the  calcium  sulphate  is 
soluble  to  a  degree  and  in  this  way  adds  to  the  perma- 
nent hardness  as  stated. 

3.  Removal  of  Permanent  Hardness.— For  removal  of 
this  in  large  plants  the  water  is  treated  writh  the  requi- 
site amount  of  sodium  carbonate  in  solution.  This  reac- 
tion then  takes  place, 

CaS04  +  Na2C03  ->  CaC03  +  Na2S04. 

The  sodium  carbonate  is  added  at  the  same  time  as  the 
milk  of  lime  previously  mentioned.  The  precipitate,  it 
will  be  noticed,  is  the  same  as  in  the  other  case;  both 
will  settle  together  and  be  removed  at  the  same  time. 
Sodium  sulphate  in  this  case  remains  in  the  water,  but 
in  small  quantities  causes  no  appreciably  bad  results. 
In  large  amounts  any  sodium  salt  would  cause  the  pre- 
cipitation of  the  soap  when  added,  from  ionic  reasons. 
This  was  found  true  when  hydrogen  chloride  was  passed 
into  a  solution  of  common  salt  to  produce  pure  sodium 
chloride.  (See  p.  309.) 

The  Permutit  System. — This  is  sometimes  called  the 
zeolite  process,  and  is  protected  by  rigid  patents.  The 
water  containing  the  calcium  or  magnesium  compounds 
is  made  to  flow  through  cylinders  containing  an  artificial 
sodium  compound  known  as  zeolite.  In  the  process  the 


350  APPLIED    CHEMISTRY 

magnesium  and  calcium  in  the  hard  water  are  removed 
by  interchange  with  the  sodium  in  the  zeolite.  It  is  said 
the  water  is  rendered  perfectly  soft.  In  the  case  of  very 
hard  waters,  however,  considerable  amounts  of  sodium 
salts  are  introduced  into  the  softened  water.  As  this  is 
objectionable,  the  water  must  be  further  treated  with 
lime  as  described  already. 

4.  Effects  of  Hardness  upon  Soap. — Without  the  soft- 
ening of  the  water  used  in  large  plants,  the  cost  of  the 
soap  item  would  be  enormous.  No  work  can  be  done  by 
soap  as  long  as  the  water  is  hard,  for  it  reacts  with 
the  compounds  of  calcium  present  thus, 

CaS04  +  2NaC17II3.,COO  ->  Na2S04  +  Ca(C17H35COO)2. 
The  equation  shows  by  the  interaction  that  a  calcium 
stearate  is  formed,  a  species  of  soap,  which  is  insoluble 
in  water,  and  floats.  It  forms  the  disagre?able,  greasy- 
feeling  scum  upon  such  waters  and  adhering  to  the  sides 
of  the  bath  tub.  In  laundry  work  it  sticks  to  the  clothing 
and  under  the  hot  iron  it  melts  like  wax  and  is  thus  spread 
out  upon  the  garment  as  a  dark  gray  or  dirty  looking  spot. 
So  with  hard  water,  aside  from  the  expense,  high  quality 
work  in  a  laundry  is  impossible.  When  the  soap  has 
combined  with  all  the  calcium  salts  present  in  the  water 
then  it  can  begin  to  form  emulsions  for  the  removal  of 
the  foreign  matter  from  the  clothing,  but  not  before.  In 
all  cities  using  hard  water  the  soap  bill  is  a  constant 
tax  upon  the  people.  In  Glasgow,  Scotland,  a  few  years 
ago,  a  change  was  made  from  the  hard  water  supply  which 
had  been  used  for  years  to  one  much  softer.  In  the 
first  year  the  saving  in  soap  bills  was  estimated'  at  $200,000. 
In  the  home,  therefore,  if  the  water  is  appreciably  hard, 
small  quantities  of  sal  soda  with  very  little  ammonia 
water  should  be  used  both  as  a  means  of  economy  and  for 
better  results.  Borax,  as  a  water  softener,  when  delicate 


HARD    WATERS METHODS    OF    SOFTENING  351 

garments  are  to  be  laundered  or  for  washing  the  hair, 
is  regarded  as  preferable  to  sal  soda.  Its  reaction  upon 
the  hard  water  is  not  essentially  different  from  that  of 
the  soda,  except  that  the  calcium  is  changed  into  a  boratc 
instead  of  a  carbonate,  thus, 

Na2B40-  +  CaS04  -»  CaB4O7  +  Na2SO4. 

5.  Degree  of  Hardness. — Hardness  in  water  is  esti- 
mated in  degrees.  Thus,  water  which  contains  1  grain, 
or  about  %5  of  a  gram,  in  a  gallon,  of  calcium  carbonate 
or  its  equivalent  of  any  other  calcium  salt  is  said  to  have 
one  degree  of  hardness.  This  is  about  the  equivalent  of 
one  part  of  calcium  carbonate  in  50,000  or  60,000  of 
water.  For  every  hundred  gallons  of  water  with  one  de- 
gree of  hardness,  between  2  and  21/2  ounces  of  soap  must 
be  used  simply  to  remove  the  hardness  before  doing  any 
cleansing.  Not  only  is  this  much  soap  wasted,  but  the 
greasy  precipitate  gathers  upon  the  clothing  as  men- 
tioned. For  a  family  of  four  it  is  estimated  that  about 
16  pounds  of  soap  would  be  required  in  a  year  to  soften 
the  water  alone.  Hardness  sometimes  reaches  as  high  as 
ten  or  even  twenty  degrees  in  which  case  the  soap  used  is 
no  small  item,  when  the  laundry  work  is  done  at  home.  If 
treated  with  sodium  carbonate,  a  little  over  !/2  ounce 
is  sufficient  to  remove  one  degree  of  hardness  from  100 
gallons  of  water;  5  or  6  pounds  would  be  sufficient  for 
laundry  and  bath  purposes  for  a  whole  year.  With 
ten  degrees  of  hardness  50  to  60  pounds  would  be  needed. 
Since  a  pound  of  sal  soda  is  very  cheap  it  becomes  a 
matter  of  great  economy  to  soften  the  water  thus  be- 
fore adding  the  soap. 

Exercises  for  Review 

1.  What  is  meant  by  hard  water?  What  two  kinds  are  there? 
Explain  the  difference?  . 


352  APPLIED    CHEMISTRY 

2.  Can  water  be   both  temporarily  and  permanently  hard?     Ex- 
plain. 

3.  What  produces  temporary  hardness?     Permanent? 

4.  What  is  boiler  scale?     Show  by  an  equation  how  it  forms. 

5.  How  may  temporary  hardness  be  removed  at  home?     On   a 
large  scale  how  is  it  done? 

6.  What  is  the  effect  upon  city  waters  of  removing  the  mud  by 
a  coagulant? 

7.  How  do  laundries  soften  the  water  for  their  wTork?     Show  by 
equations  how  they  remove  both  kinds  of  hardness. 

8.  What  is  meant  by  one  degree  of  hardness?     How  high  may 
water  run? 

9.  State  effect  of  great  hardness  upon  cost  of  living. 

10.  What  is  the  effect  of  hardness  upon  soap?    What  unpleasant 
results  follow  the  use  of  soap  in  hard  water? 

11.  Complete  these  equations: 

CaH2(CO3)2  +  soap  ->  , 
CaSO4  (heated)  ->  , 
CaS04  +  NH4HO  -»  , 
CaS04  +  Ca(HO)2  -»  , 
CaH2(C03)2  +  NH4HO  ->  , 

In  which  of  these   five   equations  is  the  water   softened  and  in 
which  not? 


CHAPTER  XXIX 
CLEANING  AND  POLISHING 

Outline- 
Necessity  for  Cleanliness 
Solutions  and  Emulsions 
Cleansing  by  Soap 

Chemistry  of 
Dry  Cleaning 
Sinks  and  Waste  Pipes 
Cleaning  Metal  Wares 

(a)   Silverware 

(&)   Copper  and  Brass 

(c)   Aluminum  Vessels 

(<f)   Nickel 

1.  Importance  of  Cleanliness. — The  great  problem  of 
modern  civilized  life  is  that  of  cleanliness.    It  is  the  one 
great  contributing  factor  of  health.    Formerly  soap  was 
used   largely   as   a   medicinal   preparation   and   not   as 
a  detergent.    Real  cleanliness  was  almost  unknown  and 
impossible :  epidemics  swept  unchecked  through  commu- 
nities.    Perfumes  were  adopted  as  disguise  for  lack  of 
cleanliness. 

2.  Emulsions  and  Solutions. — If  a  little  oil  be  shaken 
in  a  test  tube  with  some  ether,  the  oil  disappears  and 
we  have  a  homogeneous  mixture  which  is  called  a  solu- 
tion.   If  the  experiment  be  repeated  with  oil  and  water, 
the  two  may  be  mixed  by  vigorous  shaking,  but  the  oil 
soon  separates  out  and  rises  to  the  top.    Again,  if  some 
soap  be  added  to  the  oil  and  water  in  the  tube   and 
shaken  for  some  time,  the  oil  disappears  and  only  sepa- 
rates out  again  very  slowly.     Moreover,  the  resulting 
mixture  has  become  cloudy  or  even  milky  in  appearance. 

353 


354  APPLIED    CHEMISTRY 

It  is  called  an  emulsion.  Milk  is  probably  the  most  famil- 
iar example  of  emulsions  and  the  oil  in  the  form  of 
cream  only  slowly  rises  to  the  top. 

3.  Cleansing  Action  of  Soap. — Just  what  is  the  action 
of  soap  in  cleansing  by  means  of  it  is  somewhat  a  matter 
of  question.  As  a  rule  "dirt"  or  foreign  matter  ad- 
heres to  clothing  or  to  the  body  because  of  oily  matter 
present.  "Clean"  mud  when  dry  may  be  easily  brushed 
off,  but  mixed  with  grease  it  cannot.  If  in  some  way  the 
oil  or  grease  may  be  removed,  then  the  dirt  is  carried 
away  mechanically  by  the  water.  But  oils  are  not  solu- 
ble in  water,  hence  cannot  be  removed  thus.  Hot  water 
may  melt  the  grease  and  cause  more  or  less  of  it  to  float 
away,  but  even  this  is  imperfect.  The  use  of  soap  is  the 
most  common  method.  It  has  been  seen  that  in  water 
soap  is  hydrolyzed  with  the  formation  of  some  sodium 
hydroxide.  It  is  believed  by  some  that  this  free  alkali, 
especially  if  the  water  be  warm,  saponifies  the  oil  upon 
the  garment  or  body,  and  that  the  water  then  dissolves 
and  carries  it  away  together  with  the  dirt.  This  may 
occur  to  some  extent,  but  the  process  of  saponification 
is  too  slow,  apparently,  to  account  for  all  that  happens. 
What  seems  more  probable  is,  that  the  soap  forms  an 
emulsion  with  the  oil  and  that  it  is  thus  removed  to- 
gether with  the  associated  foreign  matter.  This  process 
is  fairly  rapid.  In  accordance  with  this  idea  and  to 
aid  in  the  emulsifying  of  a  solid  fat  there  are  soaps  on 
the  market  which  contain  a  considerable  percentage  of 
naphtha  or  some  other  oil.  In  laundry  work  the  naphtha 
is  believed  to  dissolve  the  grease  on  the  garment  and 
then  the  liquid  emulsifies  more  easily  with  the  soap. 
Very  hot  water  is  not  desirable  in  the  use  of  such  soaps 
as-  they  tend  to  evaporate  the  naphtha  before  it  has  dis- 
solved the  grease.  Upon  cotton  goods  soaps  with  not 


CLEANING    AND    POLISHING  355 

over  1  per  cent  of  free  alkali  may  be  used  without  seri- 
ous results;  for  woolens  and  for  toilet  purposes  there 
should  be  none  present.  For  rough  cleaning,  as  of  floors, 
unfinished,  free  alkali  in  soap  is  not  objectionable,  but 
upon  painted  or  varnished  surfaces  it  is  injurious. 

4.  Dry  Methods  of  Cleaning-. — Sometimes  the  nature 
of  the  fabric  does  not  admit  of  the  use  of  soap  and  wa- 
ter.    In  such  cases,  sometimes,  it  is  possible  to  remove 
the  grease  by  heat  and  an  absorbent.    Below  the  spot  is 
placed  a  sheet  of  blotting  paper  or  Fuller's  earth,  or 
French  chalk,  or  some  similar  porous  agent.    A  hot  iron 
applied  above  will  melt  the  grease  and  tend  to  expel"  it. 
Then  it  will  be  largely  taken  up  by  the  absorbing  agent. 
In  ordinary  dry  cleaning  a  volatile  solvent  is  used.     The 
oil  is  dissolved  out  of  the  garment  and  the  foreign  matter 
washed  away  mechanically.     Ether  is  one  of  the  most  ex- 
cellent solvents  known  for  oils  and  fats,  but  it  is  too  ex- 
pensive for  ordinary  use;  moreover,  it  is  very  inflamma- 
ble.    Carbon  tetrachloride  is  also  an  excellent  solvent  for 
oils,  and  is  not  inflammable,  hence  perfectly  safe.     It  is 
more  expensive,  however,  than  some  other  agents.     Ben- 
zine and  gasoline  are  both  good  solvents  for  oils  and  are 
the  most  commonly  used  on  account  of  their  cheapness. 
However,  they  are  very  inflammable,  and  carelessly  han- 
dled are  the  cause  of  many  explosions  and  fires. 

Painters  and  workmen  about  oily  machinery  ordinarily 
remove  the  dirt  from  their  hands,  first  by  some  solvent. 
Kerosene  or  gasoline  upon  " waste7'  will  dissolve  the  lin- 
seed oil  in  the  paint  or  the  grease  as  the  case  may  be,  and 
soap  will  finish  the  process. 

5.  Ink  and  Other  Stains. — Ordinary  black  ink  since 
it  is  made  from  green  vitriol  and  nutgalls  may  be  re- 
moved by  applying  a  solution  of  oxalic  acid  in  water. 
Usually  a  few  minutes  is   sufficient.     The  spot  should 


356  APPLIED   CHEMISTRY 

be  washed  with  water  afterward.  Other  black  inks  may 
generally  be  removed  from  clothing  by  moistening  the 
spot  with  a  solution  of  bleaching  powder  in  water.  Af- 
ter allowing  to  stand  a  few  minutes,  add  vinegar  and 
wash  with  water.  Violet  and  other  anilin  inks  may 
usually  be  removed  with  bleaching  powder  solution 
without  great  difficulty.  But  it  must  be  remembered 
that  this  method  cannot  be  used  upon  a  colored  article, 
as  it  will  be  bleached. 

From  the  common  use  of  red  ink  in  bookkeeping  acci- 
dents sometimes  occur.  For  the  removal  of  such  stains  a 
mixture  of  about  twenty  parts  of  denatured  alcohol  with 
one  of  nitric  acid  is  recommended. 

Iron  rust  may  generally  be  removed  by  moistening 
with  citric  acid  or  lemon  juice  and  exposing  to  bright 
sunlight.  Usually  one  treatment  is  sufficient.  Indelible 
inks,  which  usually  or  often  contain  silver  nitrate,  may 
be  removed  by  a  solution  of  ammonium  chloride  and  cor- 
rosive sublimate — 10  grams  of  each  in  80  c.c.  of  water. 
This  should  be  rubbed  on  with  a  soft  cloth.  Lunar 
caustic  stains  upon  the  hands  may  thus  be  removed. 

Fresh  paint  upon  clothing  may  be  removed  by  apply- 
ing turpentine  or  benzine,  better  with  a  cloth  or  blotter 
beneath  to  absorb  the  oil.  Old  or  dried  paint  on  wood- 
work may  be  removed  by  applying  a  mixture  of  aqua 
ammonia  and  a  25  per  cent  solution  of  sodium  hydrox- 
ide, one  part  each,  with  five  parts  of  water  glass.  Allow 
it  to  remain  on  the  wood  till  the  paint  has  softened,  then 
wipe  off. 

Pencil  marks  and  soiled  spots  upon  tracing  cloth  may 
be  wiped  off  with  benzine  upon  a  soft  cloth,  without 
affecting  the  ink  drawing  at  all.  Oily  stains  upon  wall 
paper  may  often  be  removed  by  applying  a  paste  of 
kaolin  and  water  or  magnesia  in  benzine  and  allowing 


CLEANING   AND    POLISHING  357 

to  remain  about  twelve  hours.  Then  rub  off  gently  with 
a  soft  cloth.  Sometimes  a  second  application  is  neces- 
sary. 

Nitric  acid  stains  upon  the  hands  are  very  difficult  of 
removal.  One  of  the  best  plans  is  to  apply  a  strong  so- 
lution of  potassium  permanganate  and  after  a  few  min- 
utes wash  off.  with  hydrochloric  acid,  about  5  per  cent 
in  strength. 

6.  Cleaning  Waste  Pipes. — It  often  happens  that  waste 
pipes  from  kitchen  sinks  becomes  more  or  less  clogged 
so  that  water  is   only  carried  aAvay   slowly,   if  at  all. 
This  is  usually  largely  the  result  of  carelessness.     The 
grease  removed  from  the  dishes  by  hot  water  and  soap 
becomes  solid   again  when  the  water  is   cooled  in  the 
trap,  and  adheres  to  the  waste  pipe.     If  coffee  grounds 
or  other  similar  solids  are  poured  into  the  sink  they  are 
caught  by  the  grease  and  in  course  of  time  fill  the  trap 
and  waste  pipes.    If  care  is  taken  never  to  put  any  such 
solid  material  into  the  sink  there  will  seldom  be  any 
trouble.     The   grease   may  solidify  upon  the   pipe   but 
the  alkali  formed  by  the  hydrolysis  of  the  soap  and  from 
the  washing  powders  will  gradually  saponify  it  and  re- 
move it.     Especially  will  this  be  true  if  occasionally  a 
spoonful  or  two  of  some  washing  powder  be  dropped 
into  the  strainer  of  the  sink  and  allowed  to  stand  in 
the  trap  over  night.     In  very  bad  cases  some   caustic 
soda  or  lye  dropped  upon  the   strainer   and  left   over 
night  will  generally  open  up  the  pipe  so  that  warm  wa- 
ter will  clean  it  out,  without  the  aid  of  the  plumber. 

7.  Cleaning  Metal  Surfaces. — Most  metals  exposed  to 
the  air  if  moisture  be  present  become  tarnished  either 
through  the  action  of  the  oxygen  or  because  of  some 
other   gas   present   in   the    atmosphere.      Upon    articles 
commonly  used  in  the  home  this  action  is  relatively  slow 


358  APPLIED    CHEMISTRY 

as  a  rule,  so  that  only  in  the  course  of  weeks  does  it 
become  appreciable.  In  the  case  of  silverware,  the  coat- 
ing is  a  sulphide ;  usually  with  other  metals  it  is  some 
form  of  oxide.  Obviously,  anything  which  would  dis- 
solve the  oxide,  or  sulphide,  would  remove  it  and  leave 
the  surface  as  bright  as  before.  Frequently,  however, 
a  reagent  that  will  dissolve  the  film  will  also  react  with 
the  metal  itself.  Hence,  great  care  must  be  exercised 
in  the  use  of  such  cleaning  agents.  In  the  case  of  sil- 
verware, the  sulphide  coating  is  readily  soluble  in  a  so- 
lution of  potassium  cyanide  and  may  be  quickly  removed 
in  that  way.  But  since  potassium  cyanide  is  a  most 
violent  poison,  its  sale  is  restricted  and  this  method  is 
not  suited  to  the  home.  All  small  silver  articles,  such 
as  knives,  forks  and  spoons,  may  be  readily  cleaned  by 
putting  them  into  some  aluminum  vessel,  covering  with 
water  and  warming  for  a  few  minutes.  Some  think  the 
addition  of  a  little  salt  is  helpful.  As  aluminum  is  much 
more  electropositive  than  the  silver,  the  sulphur  is  thus 
removed  from  the  less  positive  metal  and  it  is  left  clean 
and  bright.  There  are  many  silver  polishes  to  be  had 
on  the  market,  but  they  require  more  work  and  time  and 
are  more  harmful  to  the  silverware.  A  home-made 
powder,  which  is  good  and  harmless,  may  be  made  of  the 
following  common  substances, 

Prepared  chalk,  3  parts, 
Tartaric  acid,  3  parts, 
Powdered  alum,  1  part. 

Oxalic  or  citric  acid  may  be  substituted  for  the  tartaric. 
The  oxalic  is  usually  the  cheapest.  Lemons  contain  citric 
acid.  All  must  be  finely  powdered  and  well  mixed 
together.  The  mixture  is  to  be  applied  with  a  soft, 
damp  cloth. 


CLEANING    AND    POLISHING  359 

8.  Copper  and  Brass. — The  film  of  oxide  upon  copper 
and  brass  articles  is  soluble  in  ammonium  hydroxide. 
Usually,  therefore,  polishes  made  for  such  surfaces  con- 
tain some  ammonia.     Venetian  red,  rouge,  whiting,  or 
any  similar  powder,  mixed  with  water  and  a  little  am- 
monia work  well  upon  these  metals.     It  is  necessary  in 
using-  such  a  polish,  to  wipe  the  surface  perfectly  dry 
and  clean  at  the  close,  for  the  alkali  also  attacks  the 
metal  and  if  left  would  cause  it  to  tarnish  again  and 
quickly.     Polished  brass  articles  are  usually  protected 
by  a  thin  coat  of  lacquer.     This  is  made  by  dissolving 
shellac  in  alcohol.     It  is   applied  by  means   of  a   soft 
brush. 

9.  Aluminum  Ware. — Kitchen  ware  made  of  aluminum 
does  not  tarnish  readily,  and  usually  nothing  more  than 
ordinary  cleanliness  is  needed  to  keep  it  in  good  shape. 
Putty   powder,   whiting   or   rouge   mixed   with   a   little 
oil  are  good  for  polishing  if  needed.     The  addition  of 
some  organic  acid  like  the  juice  of  lemon  or  oxalic  may 
be  helpful.     Strong  alkalies  attack  aluminum  readily; 
hence,  washing  powders  that  contain  free  sodium  hy- 
droxide, as  many  of  them  do,  should  be  used  only  spar- 
ingly and  not  left  to  stand  in  the  vessel. 

10.  Nickel  and  Other  Metals. — Nickel  plated  surfaces 
may  be   cleaned  by   polishing   with   whiting   or   rouge, 
mixed  with  some  organic  acid.     Vinegar  or  oxalic  are 
good.     Iron  vessels  are  so  readily  attacked  by  oxygen 
in  moist  air  that  they  are  not  used  unprotected.     The 
various  methods  for  preserving  such  surfaces  are  men- 
tioned elsewhere.     For  tin  cans,  tin  plate  is  used,  for 
which,    see    page   403.      For    larger    articles,    steel    plate 
is  galvanized,  mentioned  on  p.  384.     For  cooking  vessels 
much  " granite  ware"  is  still  used.     Kitchen  stoves  are 
protected  often  by  enamels,  baked  on  at  intense  heat. 


obU  APPLIED    CHEMISTRY 

These  may  gradually  wear  off,  when  they  should  be 
replaced  by  a  prepared  article  to  be  had  at  hardware 
and  automobile  supply  houses.  Heating  stoves  are  usu- 
ally protected  by  a  thin  film  of  magnetic  oxide  of  iron, 
put  on  by  treating  the  metal  with  superheated  steam. 
This  gives  the  surface  a  bluish  color.  It  is  sometimes 
spoken  of,  in  the  case  of  stove-pipe  especially,  as  "Rus- 
sia iron."  This  film  adheres  firmly  and  is  fairly  durable. 
Such  surfaces  do  eventually  rust,  however.  Prepared 
polishes  usually  containing  graphite,  are  applied  and 
polished  by  rubbing  briskly  with  a  stiff  brush.  Liquid 
polishes  are  to  be  had  which  dry  with  a  gloss  and  need 
no  rubbing,  but  often  they  burn  off  at  the  first  heating 
and  are  of  little  value. 

Exercises  for  Review 

1.  What  is  an  emulsion?     How  is  it  different  from  a  solution? 
Illustrate. 

2.  Name  some  very  common  emulsion.     How  may  an  emulsion  of 
soap  and  kerosene  be  made? 

3.  Give  the   cause  for   dirt   adhering  to   clothing.     What  is  the 
theory  underlying  the  cleaning  of  clothing? 

4.  Give  two  theories  regarding  the  cleansing  action  of  soap. 

5.  Which  is  the  more  plausible  of  these  theories?     Wherein  lies 
the  value  of  a  soap  containing  naphtha? 

6.  WThy  arc  soaps  with  free  alkali  objectionable  with  woolens? 
Why  do  they  make  the  hands  chap? 

7.  Describe  one  method  of  removing  a  grease  spot  from  a  gar- 
ment by  heat. 

8.  Give  the  usual  method  of   dry  cleaning.     What  is  the  prin- 
ciple involved? 

9.  Name  the  solvents  that  might  be  used  in  dry  cleaning.     What 
advantage  has  each?     Why  is  benzine  commonly  used? 

10.  What  is  the  best  means  of  cleaning  the  hands  when  badly 
soiled  by  working  about  machinery? 

11.  What  kinds  of  soaps  should  be  used  upon  finished  woodwork, 
if  any?     Why  do  you  say  so? 


CLEANING   AND   POLISHING  361 

12.  What    is    usually    the    cause    of    stoppage    in    wastepipes    in 
kitchen  sinks  1     How  may  they  be  kept  clean? 

13.  If    already    stopped,   how   may    a   waste    pipe    as   a   rule   be 
opened? 

14.  What  is  the   cause  usually  of  metals  tarnishing?     What   in 
the  case  of  silverware? 

15.  Give    some    easy   way    of    cleaning    small    articles    of    silver. 
Explain  the  chemical  action. 

10.  How  is  brass  usually  protected  against  tarnish?     What   do 
most  copper  and  brass  polishes  contain?     Why? 

17.  Why  do  tomatoes,  rhubarb,  and  similar  articles  of  food  tend 
to   keep    aluminum   cooking   vessels    bright?      Why   should    strongly 
alkaline  washing  powders  not  be  used  much  upon  aluminum  ware? 

18.  How  may  one  know  by  the  feeling  in  water  whether  a  wash- 
ing powder  contains  much  free  caustic  soda? 

19.  Name  some  ways  of  protecting  the  iron  used  in  the  home. 
What  is  Russia  iron?     How  are  stoves  usually  polished?     Why  is 
this  substance  commonly  used? 


CHAPTER  XXX 
THE  COPPER  GROUP 

Outline- 
Members  of  the  Group 
Copper 

(«)   Occurrence 
(6)   Characteristics 

(c)  Uses 

(d)  Alloys 
Compounds 

(«)   Blue  Vitriol 
(&)   Other  Compounds 
Silver 

(a)  Occurrence 

(b)  Characteristics 

(c)  Uses 

(d)  Compounds 

(a)  Silver  Nitrate 

(6)  Silver  Chloride 

(c)  Silver  Bromide 
Photography 

(fl)  Principles  Involved 

(&)  Developing 

(c)  Printing 

(d)  Kinds  of  Papers 

(e)  Blue  Prints  ' 
Gold 

(a)   Occurrence 

(6)   Methods  of  Mining 

(c)  Characteristics 

(d)  Uses 

1.  Members  of  the  Group. — To  this  group  belong  three 
metals  all  of  which  are  found  free  in  nature.  For  this 
reason  they  have  been  known  from  most  remote  times. 
Moreover,  all  are  soft  metals,  hence  easily  worked  even 

362 


THE    COPPER    GROUP  363 

without  any  great  advancement  in  scientific  processes. 
They  are  often  spoken  of  as  the  "noble  metals,"  a  term 
applied  to  all  which  may  be  separated  from  their  ores 
by  heat  alone.'  In  the  periodic  table  they  are  found  at 
the  left  hand  in  the  same  division  as  sodium  and  potas- 
sium. It  will  be  noticed,  however,  that  they  are  placed 
on  the  right  side  of  this  column  and  not  under  the  alka- 
li metals.  In  the  study  of  the  table  it  was  said  that  the 
metals  seemed  to  arrange  themselves  in  octaves  and 
that  those  with  the  same  properties  occur  at  intervals 
of  eight.  It  should  be  added  here  that  after  we  pass 
potassium,  these  periods  become  double  octaves ;  that  is, 
leaving  potassium,  a  single  octave  brings  us  to  copper 
which  is  so  different  from  the  alkali  metals  that  it  was 
placed  at  the  right  of  the  space  as  a  member  of  another 
family;  again  proceeding,  another  octave  brings  us  to 
an  alkali  metal  which  is  placed  under  sodium.  In  this 
way,  copper,  silver  and  gold  are  at  the  center,  as  it  were, 
of  three  long  periods  or  double  octaves,  and  are  classed 
together.  In  many  ways  they  are  alike ;  in  other  respects, 
they  are  dissimilar ;  but  in  nearly  all  their  properties  they 
are  utterly  unlike  the  alkali  metals.  Silver  has  a  valence 
of  one;  copper  is  usually  regarded  as  bivalent,  although 
it  forms  unsaturated  compounds  where  it  appears  as  if 
univalent.  Gold  is  trivalent,  but  forms  one  or  more  com- 
pounds in  which  it  appears  as  if  univalent.  They  are  all 
malleable,  ductile,  and  good  conductors  of  electricity. 

2.  Occurrence  of  Copper. — By  the  Greeks  and  ancient 
Phoenicians  copper  was  obtained  from  the  mines  upon 
the  island  of  Cyprus.  This  gave  the  metal  its  name,  kup- 
rum,  from  which  it  derived  the  symbol.  In  America  the 
longest  known  deposits  are  those  of  the  Lake  Superior 
and  Michigan  regions.  From  copper  vessels  found  in  the 
mounds  of  prehistoric  tribes  it  is  known  that  they  were 


364  APPLIED    CHEMISTRY 

familiar  with  these  deposits.  The  outcropping  metal  was 
in  thin  sheets  between  layers  of  rock.  By  cracking  this 
off,  sometimes  by  heavy  stones,  sometimes  apparently  by 
fire,  the  thin  sheets  were  obtained  and  beaten  into  rude 
vessels.  These  deposits  are  still  valuable  and  some  of  the 
mines  as  the  Calumet  and  Hecla,  though  at  a  depth  of  a 
mile  or  more,  are  still  heavy  producers.  The  copper  in 
this  region  is  mostly  pure  and  is  separated  from  the  rock 
mechanically. 

Western  Deposits. — In  several  of  the  western  states,  es- 
pecially Montana,  Colorado,  Arizona  and  New  Mexico, 
copper  occurs  mostly  in  the  form  of  compounds  of  great 
variety.  Many  of  them  are  sulphides  having  different 
content  of  sulphur,  and  known  under  a  variety  of  names. 
Such  are  bornite,  copper  glance,  peacock  ore,  and  calcho- 
pyrite.  Two  basic  carbonates,  called  azurite,  deep  blue 
in  color,  and  malachite,  a  deep  green,  are  known. 

3.  Characteristics  of  Copper. — Copper  is  a  red  metal 
with  a  specific  gravity  of  about  11,  and  melts  at  a  tem- 
perature of  about  1,090°  C.  It  tarnishes  somewhat  in 
damp  air,  but  since  the  film  of  oxide  adheres  firmly  to 
the  metal  the  oxidation  is  merely  superficial.  In  the 
presence  of  much  moisture  carbon  dioxide  is  also  taken 
up  from  the  air  forming  a  greenish  compound  of  basic 
copper  carbonate.  It  is  a  very  tenacious  metal,  mallea- 
ble and  ductile.  Wires  may  be  made  of  a  diameter  but 
little  greater  than  1/1000  of  an  inch  of  which  a  length 
measuring  a  half  mile  would  only  weigh  about  5  grams. 
It  does  not  decompose  either  sulphuric  or  hydrochloric 
acids  in  the  cold,  for  the  reason  that  it  is  well  down  the 
electromotive  series  of  metals  as  shown  on  p.  65.  It 
does  decompose  nitric  acid  rapidly,  because  of  its  ready 
union  with  oxygen.  It  is  an  excellent  conductor  both 
of  heat  and  electricity. 


THE    COPPER   GROUP  365 

4.  Uses  of  Copper. — Copper  has  many  and  varied  uses. 
Because  of  the  fact  that  it  tarnishes  only  on  the  surface 
it  is  valuable  for  cornice  work,  roofing  and  guttering 
and  is  frequently  so  used.  For  the  same  reason  it  is 
often  used  as  a  covering  for  hulls  of  vessels.  Its  great 
conductivity  for  electricity  together  with  its  tenacity 
gives  it  use  for  wiring  houses  for  electric  lighting,  for 
telephone  circuits  and  a  great  variety  of  other  electrical 
uses.  Being  an  excellent  conductor  of  heat  renders  it 
valuable  for  stills  and  boilers,  and  for  cooking  vessels. 
It  is  almost  universally  used  in  candy  factories,  for  the 
reason  that  the  syrup  scorches  much  less  readily  in  a 
copper  vessel  than  in  most  others.  This  is  because  the 
heat  is  distributed  quickly  and  evenly  over  the  surface, 
while  in  an  iron  vessel,  or  one  of  porcelain  ware,  the 
bottom  is  very  much  hotter  than  the  sides.  In  large 
establishments  where  great  quantities  of  food  must  be 
prepared  as  in  asylums  and  penitentiaries,  or  in  res- 
taurants like  the  railway  eating  houses  wThere  the  service 
must  be  very  rapid,  copper  vessels  are  used  almost  ex- 
clusively. Such  vessels  would  probably  find  use  also  in 
the  home  were  it  not  for  the  fact  that,  while  such  strong 
acids  as  sulphuric  and  hydrochloric  are  not  decomposed 
by  copper,  it  does  react  with  many  fruit  acids,  such  as 
those  found  in  tomatoes,  apples  and  the  like.  Since 
the  compounds  resulting  are  poisonous,  it  is  not  desira- 
ble. In  large  establishments,  such  of  the  vessels  as  are 
used  with  acid  foods  are  "tinned"  on  the  inside.  As 
this  wears  off  it  has  to  be  replaced.  In  the  form  of  al- 
loys, copper  is  used  in  large  quantities.  Gold  and  silver 
coins, are  10  per  cent  copper;  brass  contains  zinc  and 
copper,  a  common  variety  having  65  per  cent  of  the  for- 
mer to  35  of  the  latter.  Bronze  consists  of  copper  and 
tin;  German  silver  of  copper  zinc  and  nickel. 


366  APPLIED    CHEMISTRY 

5.  Blue  Vitriol. — This  compound  of  copper,  often  called 
Hue-  stone,  is  mainly  a  by-product  of  the  large  gold  and 
silver  refineries.  Small  portions  of  copper  in  the  form 
of  a  sulphide  occur  mixed  with  the  other  metals; 
in  a  specially  constructed  furnace  to  which  air  is  ad- 
mitted the  copper  sulphide  is  oxidized  to  copper  sulphate. 
This  is  treated  with  water  and  dissolved  out,  is  filtered 
and  evaporated  to  the  point  of  crystallization.  Formerly, 
a  very  considerable  portion  of  that  used  in  the  United 
States  was  made  in  the  Argentine  smelter  at  Kansas 
City,  with  a  monthly  output  of  1,800  tons.  After  the 
consolidation  of  the  various  refining  companies,  this 
work  was  transferred  to  the  plants  at  Omaha  and  Den- 
ver. Blue  vitriol  crystallizes  with  five  molecules  of 
water.  Exposed  to  the  air  it  gradually  loses  this,  be- 
comes white  and  crumbles  to  a  powder.  By  adding  wa- 
ter the  color  is  restored,  and  upon  crystallizing  the 
pentahydrate  is  again  obtained.  Its  solution  gives  an 
acid  reaction  with  litmus  owing  to  hydrolysis.  (See  p. 
313.)  Like  other  salts  of  copper  it  is  very  poisonous. 

6.  Electrotyping. — Blue  vitriol  is  used  extensively  in 
making  electrotypes  for  printing  books  and  magazines. 
The  type  is  set  up,  proof  read  and  locked  in  a  frame 
or  "form"  the  size  of  the  page  to  be  printed.  An  im- 
pression of  this  is  taken  in  a  sheet  of  prepared  wax  and 
this  is  covered  with  finely  powdered  graphite  to  make  it 
a  conductor  of  electricity.  This  is  then  suspended  at  the 
cathode  in  a  solution  of  blue  vitriol.  A  sheet  of  copper 
forms  the  anode  (Fig.  63).  When  the  battery  is  con- 
nected, copper  is  slowly  deposited  upon  the  graphite 
covered  face  of  the  wax.  When  the  deposit  has  attained 
the  thickness  of  a  good  visiting  card,  the  sheet  is  re- 
moved from  the  solution,  washed  thoroughly  and  dried. 
Molten  type  metal  is  then  poured  upon  the  back  of  the 


THE    COPPER    GROUP 


367 


Copper.  This  melts  off  the  wax  and  gives  a  copper  plate 
the  exact  duplicate  of  the  lead  type  used  to  make  the 
imprint  upon  the  wax.  All  books  are  printed  from 
such  electrotypes;  likewise,  "patent"  advertisements 
which  are  run  in  the  large  dailies  of  all  the  cities,  and 
wherever  a  very  large  number  of  copies  is  desired.  Lead 
type  is  so  brittle  that  it  will  permit  of  only  a  relatively 
limited  number  of  impressions  with  perfect  results.  By 
a  similar  method  is  made  pure  electrolytic  copper  for 
which  in  limited  amounts  there  are  many  demands.  To 
obtain  this  the  impure  copper  is  suspended  from  the 


J 

, 

\~ 

copper  _wax 
Ano    —  jbeef 

CuS04   ^olufiof7 

1 

Fig.    63. — Making   an    electrotype. 

anode  and  a  very  thin  sheet  of  pure  copper  at  the  cathode. 
As  the  copper  ions  from  the  blue  vitriol  solution  deposit 
upon  the  thin  sheet  at  the  cathode,  the  sulphate  ions 
dissolve  the  impure  copper  bar  at  the  anode  and  thus  keep 
the  vitriol  solution  concentrated.  Thus,  gradually,  all 
the  copper  at  the  anode  may  be  transferred  to  the  cathode 
where  it  is  deposited  pure  electrolytic  copper,  while  the 
impurities  remain  in  solution  or  precipitate  out.  Blue 
vitriol  has  also  found  wide  use  in  "crow-foot"  and  other 
similar  wet  batteries  for  telegraphic  work ;  its  use  in  pre- 
venting the  growth  of  algae  in  water  reservoirs  has  been 


368  APPLIED    CHEMISTRY 

mentioned.     It  is  also  used  extensively  for  making  bor- 
deaux mixture  for  spraying  trees. 

7.  Some  Other  Compounds. — Copper  forms  many  other 
salts;   for   example,   cupric   chloride,    CuCl2.2H20   of   a 
beautiful  turquoise  blue  color;  cupric  nitrate,  Cu(N03)2 
.6H20,  dark  blue  in  color,  and  very  deliquescent;  cop- 
per acetate,   Cu(C2H302)2H20,  green  in  color.     It  also 
forms  cuprous  salts,   such  as  cuprous   chloride,   Cu2Cl2, 
white  in  color,  and  very  unstable.     In  the  presence  of 
air  and  moisture  this  rapidly  takes  up  oxygen  and  forms 
a  basic  cupric  chloride.     There  are  two  oxides,  cupric 
and  cuprous,  with  the  formulas,  CuO  and  Cu20.     The 
former  is  black  and  the  latter  red  in  color. 

8.  Occurrence  of  Silver.— Silver  is  often  found  free, 
sometimes  in  nuggets  of  considerable  size.    Most  copper 
ores  contain  more  or  less  silver,  but  the  greater  part 
of  our  supply  is  obtained  from  the  lead  smelters  in  the 
treatment  of  argentiferous  lead  ores. 

9.  Characteristics  of  Silver.— Silver  is  one  of  the  whit- 
est of  the  metals  and  the  best  in  conductivity.     It  has 
a  melting  point  of  about  960°  C.,  a  little  more  than  100 
below  that  of  copper.     It  does  not  oxidize  in  the  air 
at  any  temperature,   but   readily  reacts  with  hydrogen 
sulphide.     As  this  frequently  occurs  in  the  air  from  the 
combustion  of  coal  or  coal  gas,  or  from  the  decomposi- 
tion of  various  proteins  containing  sulphur,   silverware 
commonly  becomes  tarnished.    While  silver  will  not  com- 
bine with  oxygen  even  at  high  temperatures,  above  its 
melting  point,  it  will  absorb  more  than  twenty  times  its 
own  volume  of  oxygen  from  the  air.    When  solidification 
takes  place  this  occluded  oxygen  is  given  off  again  rap- 
idly,  causing  the  silver   surface  to   "spit"   and  become 
rough.     It  is  even  more  ductile  than  copper,  such  that 
wires  a  mile  and  a  quarter  in  length  will  weigh  only  about 


THE   COPPER  GROUP  369 

1  gram.  Silver  is  not  attacked  by  alkalies  or  by  hydro- 
chloric acid  or  cold  sulphuric.  Nitric  acid  is  readily  de- 
composed and  also  boiling-hot,  concentrated  sulphuric. 

10.  Uses   of  Silver. — Everyone   is  familiar   with   the 
uses  of  silver.     Thermos  bottles  and  Dewar  bulbs,  men- 
tioned elsewhere,   and  the   better   class   of  mirrors  are 
silvered  by  the  reaction  of  a  reducing  agent  with  a  sil- 
ver salt.     Formaldehyde  or  Rochelle  salt  in  the  presence 
of  an  alkali  is  often  used  for  this  purpose.    The  process 
may  be  easily  illustrated.     If  a  few  cubic  centimeters 
of  a  solution  of  silver  nitrate  be  put  into  a  test  tube  and 
ammonium   hydroxide   added   drop   by   drop   until   the 
brown  precipitate  which  forms  at  first  is  just  dissolved, 
upon  adding  a  little  tartaric  acid  and  warming,  the  tube 
on  the  inside  is  beautifully  silvered.     Our  silver  coins  are 
90  per  cent  silver.    "Sterling"  silver  does  not  mean,  as 
many  suppose,  pure  silver,  but  of  the  same  degree  of 
fineness  as  English  coins,  which  are  925  parts  of  silver 
to  75  of  copper.    Most  of  the  silverware  in  common  use 
is  merely  some  harder  metal  or  alloy  plated  with  silver. 
The  process  is  the  same  as  that  described  for  copper 
plating.    A  sheet  of  silver  is  suspended  at  the  anode  and 
the  article  to  be  plated  at  the  cathode.     A  solution  of 
potassium  silver  cyanide  takes  the  place  of  the  copper 
sulphate.     In  the  case  of  silver,  the  nitrate,  the  most 
common  silver  salt,  does  not  give  a  deposit  that  adheres 
well. 

11.  Silver  Nitrate,  AgN03. — This  compound  may  be 
prepared    by    dissolving    silver    in    nitric    acid.     Nitric 
oxide  and  water  are  the  two  other  products  formed,  as 
is  usually  the  case  when  a  metal  decomposes  nitric  acid. 
This  is  seen  in  the  equation, 

3Ag  +  4HN03  ->  3AgN03  +  NO  +  2H20. 
Silver  nitrate  crystallizes  in  thin,  flat  plates,  rhombic  in 


370  APPLIED    CHEMISTRY 

shape,  colorless  and  transparent.  Commercially,  it  is 
sold  for  medical  purposes  in  small  round  sticks  under 
the  name  "lunar  caustic."  These  usually  contain  a 
small  percentage  of  silver  chloride.  It  has  caustic  prop- 
erties and  is  used  for  this  reason  in  cauterizing  wounds, 
such  as  dog  bites,  and  others  presumably  infected.  In 
solution  it  is  sometimes  used  for  sore  throat  and  other- 
wise as  an  antiseptic.  Exposed  to  light,  especially  in 
contact  with  organic  matter,  it  turns  dark.  On  this 
account  it  is  a  constituent  of  many  indelible  inks  used 
in  laundry  marking;  also  of  most  hair  dyes,  and  as  the 
source  of  the  silver  compounds  used  in  photography. 

12.  Silver  Chloride,  AgCl. — If  a  solution  of  common 
salt  be  added  to  one  of  silver  nitrate,  silver  chloride  is 
produced,  thus, 

AgN03  +  NaCl  -»  AgCl  +  NaN03. 

It  is  a  curdy  white  precipitate,  especially  if  shaken  vig- 
orously ;  it  rapidly  turns  dark  when  exposed  to  sunlight. 
It  is  very  soluble  in  ammonium  hydroxide,  forming  a 
complex  silver  salt  resembling  the  hydrates.  Thus, 

AgCl  +  2NH4HO  -»  AgC1.2NH3  +  2H20. 

Silver  chloride  is  used  extensively  in  preparing  one  class 
of  photographic  papers  which  will  be  studied  later. 

13.  Silver  Bromide,  AgBr. — This  compound  is  made 
by  adding  to  a  solution  of  silver  nitrate  one  of  potassium 
or  ammonium  bromide,  thus, 

AgN03  +  NH4Br  ->  AgBr  +  NH4N03. 

It  is  a  very  pale-yellow  precipitate,  much  less  soluble 
in  ammonium  hydroxide  than  is  the  chloride.  It  is  much 
more  sensitive  to  light.  For  this  reason  it  is  employed  in 
photography  for  very  rapid  work  both  on  plates  and 
films,  as  well  as  for  papers  and  enlargements. 


THE    COPPER   GROUP  371 

14.  Photography. — Most  everyone  is  interested  more 
or  less  in  photography,  yet  but  few  do  much  more  than 
"press  the  button."  In  sensitizing  plates  and  films  a 
solution  of  silver  nitrate  and  one  of  ammonium  or  po- 
tassium bromide  are  added  to  one  of  gelatine,  whereupon 
the  reaction  shown  above  takes  place.  The  emulsion  is 
kept  warm  until  the  silver  bromide  -has  formed  a  fine 
precipitate  throughout  the  entire  mass,  after  which  it 
is  allowed  to  solidify.  The  mass  is  then  cut  into  shreds 
and  treated  with  cold  water  to  dissolve  out  the  ammo- 
nium nitrate  wrhich  was  formed  as  a  by-product.  It  is 
then  dried,  melted  and  allowed  to  flow  over  the  plate, 
forming  a  thin  film.  Most  photographic  papers  used  by 
amateurs  are  made  in  a  similar  way  and  contain  the 
silver  bromide  in  a  thin  film  upon  the  paper.  On  ex- 
posure to  light,  plates  and  papers,  containing  silver  bro- 
mide in  the  film,  show  no  results.  The  plate  is  put  into  a 
solution  of  some  reducing  agent,  more  often  now  a  coal 
tar  product  such  as  metol  or  hydroquinon,  together 
with  an  alkaline  salt  such  as  sodium  carbonate.  The  re- 
ducing agent  acts  upon  the  silver  salt,  decomposes  it 
and  sets  the  silver  free.  This  occurs  much  more  rapidly 
where  the  light  has  already  'begun  the  process.  The 
operation  is  called  developing  the  plate.  Naturally,  such 
portions  of  the  landscape,  or  object  being  photographed, 
as  reflect  considerable  light  will  affect  the  silver  bromide 
the  most,  and  upon  developing  will  have  the  silver  reduced 
most  rapidly,  hence  will  become  dark.  For  this  reason, 
since  white  objects  appear  upon  the  plate  as  black  after 
development,  it  is  spoken  of  as  a  negative.  If  the  plate 
be  allowed  to  remain  in  the  developer  indefinitely  finally 
all  the  silver  is  reduced  and  the  plate  becomes  black  all 
over.  To  prevent  this,  at  the  proper  time,  known  usually 
by  the  image  beginning  to  appear  upon  the  reverse  side  of 


372  APPLIED   CHEMISTRY 

the  plate,  it  is  removed  from  the  developer,  rinsed  and 
put  quickly  into  a  solution  of  sodium  thiosulphate,  called 
"hypo."  This  is  an  excellent  solvent  for  silver  chloride 
and  bromide,  so  that  any  portions  of  these  salts  left  un- 
reduced by  the  developer  are  dissolved  out  and  thus  the 
reduction  and  darkening  of  the  plate  is  stopped.  This  is 
called  fixing  the  plate.  The  process  is  complete  when  on 
being  held  up  to  the  light  no  white  appears  anywhere  and 
the  plate  is  more  or  less  transparent.  Developing  is 
done  under  red  light.  Students  of  physics  know  that 
sunlight  consists  of  three  kinds  of  rays — light,  heat  and 
chemical  rays.  In  a  study  of  the  spectrum  it  has  been 
found  that  most  of  the  heat  rays  are  at  the  red  end 
and  most  of  the  chemic  at  the  violet  end  of  the  spectrum. 
Therefore,  light  passed  through  red  glass  or  other  red 
objects  has  most  of  the  chemic  rays  filtered  out.  Hence, 
the  sensitized  plate  is  not  affected  by  such  light. 

15.  Printing-Out  Papers. — There  are  two  kinds  of  pa- 
pers used  in  photography  in  making  the  prints.    Print- 
ing-out papers  have  a  film  containing  silver  chloride  which 
is  not  nearly  as  sensitive  to  light  as  silver  bromide.    They 
are  placed  in  a  printing  frame  under  the  negative  and  ex- 
posed directly  to  good  sunlight.     The  image  prints  out 
slowly  and  can  be  seen  as  it  appears.     When  the  proper 
degree  of  intensity  has  been  reached  it  is  fixed  and  toned. 
The  fixing  is  with  hypo  as  already  described.    The  toning 
is  done  with  gold  or  platinum  compounds  in  which  small 
portions  of  these  metals  take  the  place  of  an  equivalent 
amount  of  silver  and  give  a  richer  and  softer  print.    The 
1  i  proof ' '  which  the  photographer  furnishes  is  on  printing- 
out  paper  and  has  not  been  fixed  or  toned.    Hence,  it  is 
not  permanent,  and  exposed  to  light  soon  darkens  all  over. 

16.  Developing-  Papers. — Developing  papers,  such  as 
velox,  argo,  and  many  others  now  largely  advertised, 


THE    COPPER   GROUP  373 

contain  silver  bromide  in  the  film  of  gelatine.  They  are 
intended  to  be  printed  by  artificial  light  and  if  used  in 
daylight  it  must  be  very  much  subdued  and  the  exposure 
of  the  briefest  possible  time.  No  image  appears  upon  ex- 
posure, but  it  must  be  brought  out  as  with  plates  and  films 
by  developing.  This  fact  gives  to  such  papers  the  name 
developing  papers.  With  ordinary  electric  light  an  ex- 
posure of  from  ten  to  thirty  seconds,  depending  upon  the 
negative,  soon  learned  by  a  little  practice,  is  usually  suffi- 
cient. The  developing  is  in  the  usual  way,  but  a  stronger 
solution  is  used  and  the  image  must  come  up  quickly  and 
sharply;  if  it  does  not,  the  paper  becomes  stained  and  the 
picture  ruined.  It  is  quickly  transferred  to  the  fixing 
bath  and  after  a  few  minutes  to  a  tray  of  water  where  it 
must  be  washed  thoroughly. 

17.  Blue  Prints. — Blue  prints,  used  somewhat  for 
landscape  work,  but  mostly  by  architects  and  engineers, 
are  not  made  from  silver  compounds,  but  from  iron. 
However,  they  will  be  considered  at  this  time.  A  good 
grade  of  paper  in  a  room  with  subdued  light  is  brushed 
over  with  a  solution  of  ferric  ammonium  citrate.  This 
gives  to  the  paper  on  the  one  side  a  pale-yellow  color. 
For  use  it  is  exposed  under  a  negative  or  architectural 
drawing  to  direct  sunlight,  siiice  it  is  not  very  sensitive. 
When  the  proper  exposure  has  been  made,  which  may  be 
known  by  a  sort  of  bluish-bronze  appearance,  the  paper 
is  removed  from  the  frame,  and  submerged  in  water. 
Wherever  the  sunlight  has  been  able  to  pass  through  the 
negative  or  draAving  it  has  reduced  the  ferric  citrate  to  a 
ferrous  salt,  blue  in  color  and  not  soluble  in  wrater.  The 
water,  therefore,  washes  out  the  unchanged  yellow  ferric 
citrate  and  leaves  the  blue  in  the  paper.  Hence,  in  an 
architectural  drawing  since  the  original  lines  are  in  black, 
in  the  print  they  will  be  white  upon  a  blue  background. 


374  APPLIED    CHEMISTRY 

Blue  print  paper  may  easily  be  prepared  by  the  student 
for  his  own  use  in  the  laboratory.  Blue  prints  are  so 
simple  and  so  easily  prepared  that  many  attempts  have 
been  made  to  change  them  into  sepia  or  black  by  the 
application  of  some  reagent.  Most  formulas,  however, 
in  the  hands  of  the  amateur  give  rather  indifferent  and 
unsatisfactory  results. 

18.  Occurrence  of  Gold. — As  a  rule  gold  occurs  free  in 
nature;  in  Colorado,  however,  it  is  sometimes  found  in 
combination  with  tellurium  as  gold  telluride.    Originally, 
probably,  the  grains  or  nuggets  were  scattered  through 
veins  of  quartz  found  in  cracks  in  the  earth's  crust.    How- 
ever, as  erosion  took  place,  the  disintegrated  particles  of 
rock  and  gold  have  been  carried  down  till  now  they  are 
found  in  river  beds  and  alluvial  deposits  in  many  places. 

19.  Mining  of  Gold. — The  early  history  of  every  gold 
field  is  largely  the  same.     The  prospector  recovers  the 
coarser  particles  of  gold  by  "panning"  or  "cradling." 
This  consists  in  washing  out  by  a  rocking  motion,  usually 
in  a   stream  of  water,  the   sand  and  lighter  particles. 
From  the  heavier  particles  remaining  in  the  cradle  will  be 
obtained,    by    hand,    the    grains    and    nuggets    of    gold. 
When  the  field  becomes"  proved  as  a  valuable  producer, 
capital  comes  in  with  dredging  or  hydraulic  mining.     In 
the  latter,  streams  of  water,  brought  from  distances  up 
in  the  mountains  under  tremendous  pressure,  are  directed 
against   the   hillsides   and   other    gold   bearing   deposits, 
which   are  thus   disintegrated   and   washed   down.     The 
whole  is  made  to  flow  through  troughs  or  flumes  over  fre- 
quently  recurring   pockets   of   mercury   or   over   copper 
plates  amalgamated  with  mercury.    In  this  way,  the  gold 
particles  are  caught  by  the  mercury  and  at  intervals  the 
mercury   is  distilled   and   recovered   for   use   again.     In 
California  large  quantities  of  gold  have  been  recovered  in 


THE    COPPER    GROUP  375 

this  way;  but  from  the  fact  that  the  great  volume  of 
water  used  has  resulted  in  washing  down  over  good  agri- 
cultural lands  immense  quantities  of  sand  and  gravel, 
much  litigation  has  resulted  in  recent  years  with  the  aban- 
doning of  such  methods  in  many  places.  (Fig.  64.) 
Dredging  is  usually  employed  for  working  deposits  along 
river  beds.  For  the  purpose,  a  boat  of  considerable  size  is 
constructed  upon  the  land  to  be  dredged  near  some  river 
or  water  supply.  A  pond  is  dug  large  enough  to  contain 
the  boat  and  the  water  turned  in  to  fill  it.  A  steam  or 


Fig.    64. — Hydraulic    mining.       (From    Cook's    "A    Practical    Chemistry.") 

motor  shovel,  such  as  is  used  for  extensive  excavation 
work,  is  erected  at  one  end  of  the  boat.  This  scoops  out 
the  gravel  in  front  of  the  vessel,  swings  it  around  upon 
the  deck  and  dumps  it  where  streams  of  water  provided 
by  pumps  wash  it  off  at  the  stern  over  amalgamated  cop- 
per plates.  The  gold  is  caught  by  the  mercury  as  already 
explained.  Thus  the  pond  is  constantly  being  filled  in  the 
rear  and  dug  out  in  front  of  the  boat.  Large  tracts  of 
alluvial  deposits  are  worked  in  this  way  with  very  profit  a- 


376  APPLIED    CHEMISTRY 

ble  results.  One  of  the  best  known  sections  in  the  Califor- 
nia fields  is  that  at  Oroville.  "Quartz  vein  mining" 
is  the  term  applied  to  that  used  when  tunnels  are 
run  or  shafts  sunk  to  follow  the  veins  of  gold-bearing 
quartz.  In  such  cases,  as  the  rock  is  brought  to  the  surface 
it  is  sorted  by  hand  and  the  portions  containing  little  or  no 
gold  are  carried  by  small  cars  to  the  dump  and  constitute 
the  "tailings."  The  quartz  containing  the  gold  is  crushed 
and  the  gold  recovered  either  by  the  chlorination  or  the 
cyanide  process.  In  the  former,  the  quartz  rock  is 
roasted,  which  serves  to  bring  the  gold  to  the  surface  or 
if  it  be  in  the  form  of  the  telluride,  to  volatilize  the  tellu- 
rium and  leave  the  gold  free.  It  is  then  dissolved  by  liquid 
chlorine  or  by  treatment  with  bleaching  powder  mixed 
with  hydrochloric  acid.  From  the  solution  of  gold  chlo- 
ride thus  obtained  the  metal  is  recovered  by  precipitating 
with  ferrous  sulphate  or  oxalic  acid.  If  the  cyanide  proc- 
ess is  used,  roasting  is  not  necessary.  The  gold  is  dissolved 
in  a  solution  of  potassium  cyanide  and  precipitated  from 
this  by  zinc.  In  many  places  stamp  mills  are  now  used. 
They  consist  of  steel  cylinders  of  considerable  size  and 
weight  held  upright  by  supports.  They  are  continually 
lifted  by  machinery  and  dropped  automatically  upon  the 
quartz,  which  is  slowly  fed  upon  the  platform  or  table. 
The  continued  ' '  stamping ' '  crushes  the  rock  into  fine  par- 
ticles; a  stream  of  water  washes  it  over  amalgamated 
plates  and  it  is  recovered  as  in  the  case  of  dredging. 

20.  Characteristics  of  Gold. — Gold  is  a  soft,  yellow 
metal  with  a  specific  gravity  of  19  and  melting  point 
about  1,060°  C.-  It  is  thus  between  that  of  silver  and  cop- 
per. It  is  the  most  malleable  of  all  metals  and  in  the 
form  of  gold  leaf  is  beaten  so  thin  that  it  is  said  1,500 
sheets  together  are  no  thicker  than  an  ordinary  sheet  of 
writing  paper.  Gold  is  the  least  active  chemically  of 


THE   COPPER   GROUP  377 

the  more  familiar  metals.  It  is  not  attacked  by  oxy- 
gen or  tarnished  by  hydrogen  sulphide  in  the  air  as  is 
silver.  It  is  soluble  in  aqua  regia  in  which  it  forms 
gold  chloride,  AuCl3.  It  is  also  soluble  in  potassium 
cyanide  by  which  a  complex  potassium  auric  cyanide  is 
produced,  KCN.Au(CN)3.  Nothing  need  be  said  re- 
garding the  uses  of  gold.  When  pure  it  is  spoken  of  as 
twenty-four  carats  fine.  Ordinary  jewelry  is  not  over 
fourteen  carats  and  may  even  run  as  low  as  ten  without 
being  objectionable.  Gold  plating,  or  gilding,  uses  a 
cyanide  solution  and  the  process  is  similar  to  that  al- 
ready described  for  copper  and  silver.  American  gold 
coins  are  90  per  cent  gold  and  10  per  cent  copper. 

Exercises  for  Review 

1.  Name  the  metals  of  the  copper  group  and  state  their  position 
in  the  periodic  table.     What   is  meant  by  a  long  period  in  the 
table? 

2.  What  is  a  noble  metal? 

3.  Describe   the   deposits   of   copper   in  the   north;    in   the   west. 
Name  some  important  ores  and  give  composition. 

4.  Give  the  characteristics  of  copper. 

5.  Name  the  most  important  uses  of  copper  and   state  why  so 
used  in  each  case. 

6.  Name  three  alloys  of  copper  and  give  composition. 

7.  Give  formula  for  blue  vitriol  and  state  how  made. 

8.  Explain   how    an    electrotype    is   made.      What    advantage    is 
there  in  an  electrotype?     Give  uses  for  them.     What  is  electrolytic 
copper?     How  made? 

9.  Name  some  other  compounds  of  copper  with  formulas. 

10.  What  is  the  source  of  most  of  our  silver? 

11.  Give  chief  characteristics  of  silver. 

12.  Name  some  familiar  uses  for  silver.    How  are  mirrors  made? 

13.  How  is  silver  nitrate  made?     What  is  its  commercial  name? 

14.  Give    characteristics   of    silver   nitrate.      Also    its   chief   uses 
and  state  the  principle  underlying  each  use. 

15.  How  is  silver  chloride  made?     Use? 

16.  How  is  silver  bromide  made?     What  use  has  it? 

17.  How  are  photographic  plates  and  films  made? 


378  APPLIED    CHEMISTRY 

18.  What  is  a  negative?     Why  so  called? 

19.  Explain  the  process  of  developing  a  plate. 

20.  Name  two  kinds  of  photographic  papers.     What  is  the  dif- 
ference between  them  in  action  and  composition? 

21.  Give  process  of  making  a  print  on  each  kind  of  paper. 

22.  In  what  does  fixing  a  negative  consist?     What  reagent  is 
used  for  doing  this? 

23.  What  is  the  sensitizing  agent  in  blue  print  papers?     What 
happens  when  they  are  exposed  to  the  light?     What  does  the  wa- 
ter do? 

24.  What  can  you  say  of  the  occurrence  of  gold? 

25.  What  is  meant  by  panning?     By  hydraulic  mining? 

26.  Describe  dredge  boat  mining.     How  is  the  gold  recovered? 
What  becomes  of  the  mercury? 

27.  Of  what  does  the  chlorination  process  consist? 

28.  Give  the  chief  characteristics  of  gold. 

29.  What  are  the  two  best  solvents  of  gold? 

30.  How  is  an  article  gold  plated? 

31.  What  is  meant  by  gold  eighteen  carats  fine? 

32.  What  is  the  carat  of  the  five  dollar  gold  coin? 


CHAPTER  XXXI 

THE  MAGNESIUM  FAMILY 

Outline — 

Members  of  the  Group 
Magnesium 

(«)   Natural  compounds 

(&)   Characteristics  of 

(c)  Uses 

(d)  The  Oxide 

(c}   Other  Compounds 
Zinc 

(a)   Ores  of 
(6)   Reduction 

(c)  Characteristics  of  Zinc 

(d)  Uses 

(e)  Zinc  Sulphate 
(/)   Zinc  Chloride 
(g)   Zinc  Oxide 

Mercury 

(a)   Occurrence 
(&)   Characteristics 
(c)   Uses 

(d}   Mercuric  Oxide 
(e)    The  Chlorides 
(/)    Vermilion 

1.  General  Comparison. — Besides  magnesium,  beryl- 
lium, also  known  as  glucinum,  zinc,  cadmium  and  mer- 
cury belong  to  this  group.  Beryllium  is  the  lightest 
with  an  atomic  weight  of  9.1  and  mercury  the  heaviest 
with  a  weight  of  200.  They  all  form  compounds  with 
a  valence  of  two,  and  with  the  exception  of  mercury 
form  no  other  series.  Magnesium  in  some  of  its  reac- 
tions resembles  calcium  and  in  analytic  separations  is 
often  classed  in  that  group. 

379 


380  APPLIED    CHEMISTRY 

2.  Natural   Compounds  of  Magnesium. — Besides  the 
sulphate  found  in  sea  water  and  in  springs,  known  as 
Epsom  salt,  magnesium  chloride,  MgCl2,  is  found  asso- 
ciated with  common  salt,  and  the  double  carbonate  of 
magnesium  and  calcium,  known  as  dolomite,  occurs  with 
limestone.     Magnesium  also  is  found  in  several  natural 
silicates  of  more  or  less  complex  composition.     One  of 
the  best  known  of  these  is  meerschaum.     It  is  a  soft, 
white   mineral  used   in   making   pipes   for   which   it   is 
prized  because  of  the  brown  colors  it  assumes.     Much 
more  valuable  than  this  is  asbestos,  a  greenish,  anhy- 
drous silicate. 

This  mineral  has  a  silken  luster  and  is  fibrous,  so  that 
by  mechanical  process  it  may  be  worked  into  a  loose 
mass.  In  this  form  it  has  numerous  uses.  Mixed  with 
magnesium  oxide  it  is  employed  as  an  insulating  ma- 
terial for  steam  pipes  to  prevent  loss  of  heat  by  radia- 
tion; railway  locomotives  are  thus  jacketed;  it  is  used 
for  insulation  against  fire  in  many  ways ;  for  large  stage 
drop  curtains;  in  stoves;  about  furnaces  and  furnace 
pipes;  in  gaskets  for  steam  pipe  fittings;  brake  linings 
for  motor  cars;  as  a  cement  for  expensive  stucco  work; 
imitation  tile  and  shingle  roofing  and  in  scores  of  other 
ways. 

3.  Characteristics  of  Magnesium. — Magnesium  is  pre- 
pared much  as  is  calcium,  that  is,  by  the  electrolysis  of 
the    double    salt    of    magnesium    and    potassium,    KC1. 
MgCl2.     It   is   a   grayish   white   metal,   with   a   specific 
gravity  of  1.75.    In  the  air  it  reacts  slowly  with  oxygen 
by  which  a  thin  coating  upon  the   surface  is  formed. 
When  heated  it  burns  vigorously  with  a  brilliant  white 
light.     It  is  one  of  very  few  elements  which  combines 
directly  with  nitrogen.    When  burned  in  the  air  an  ap- 
preciable amount  of  the  product  formed  is  magnesium 


THE   MAGNESIUM   FAMILY 

nitride,  Mg3N,.  Magnesium  does  not  react  with  cold 
water,  but  will  set  free  hydrogen  from  boiling  hot  water. 
It  is  high  in  the  electromotive  series  of  metals  and  rap- 
idly decomposes  even  dilute  acids  with  evolution  of  hy- 
drogen. It  is  brittle,  but  when  heated  somewhat  it  may 
be  drawn  into  wires ;  flattened,  this  is  spoken  of  as  mag- 
nesium ribbon.  It  is  also  sold  in  the  form  of  powder. 

4.  Uses  of  Magnesium. — The  powdered  magnesium  is 
used   extensively   for  flashlight   work   in   photography. 
For  this  purpose,  sometimes  it  is  blown  into  the  flame  of 
a  specially  constructed  alcohol  lamp;  again  it  is  mixed 
with  potassium  chlorate,  which  causes  a  very  rapid  com- 
bustion of  the  whole  mass.    The  same  mixture  is  used  in 
fireworks  to  give  the  intensely  white  lights  in  the  vari- 
colored bombs.     Flashlight  powders  must  be  regarded 
as  explosives  and  handled  with  great  care.     Magnalium 
is  an  alloy  of  magnesium  and  aluminum,  light  and  tena- 
cious in  properties,   at  present  being  made  for  use  in 
air  ships  and  for  similar  work  where  a  light  metal  is 
needed. 

5.  Magnesium  Oxide,  MgO. — This  is  sold  under  the 
name  of  magnesia.    It  is  a  fine,  white  powder,  made  by 
calcining  magnesium  carbonate,  as  lime  is  prepared  from 
limestone.     The  reaction  is  the  same, 

MgC03  ->  MgO  +  C02. 

It  is  an  excellent  insulating  material  against  loss  of 
heat.  Hence,  as  stated  elsewhere,  it  is  mixed  with  as- 
bestos, about  four  parts  to  one,  as  a  covering  for  steam 
pipes  and  all  similar  places  where  loss  of  heat  is  to  be 
prevented.  Our  great  railway  locomotives,  in  cold  weath- 
er, would  never  be  able  to  make  sufficient  steam  to 
pull  a  loaded  train  were  it  not  for  the  heavy  jacketing 
of  the  boilers  with  magnesia.  Likewise,  in  refrigeration 
systems,  the  pipes  which  transmit  the  brine  from  the 


382  APPLIED    CHEMISTRY 

source  to  points  of  use  are  protected  against  access  of 
outside  heat.  For  a  similar  reason,  and  because  it  is 
infusible,  it  is  used  in  lining  electric  furnaces  and  for 
making  crucibles  where  great  heat  is  to  be  employed. 

6.  Other  Compounds. — Magnesium  sulphate,  sold  un- 
der the  name  of  Epsom  salt,  is  a  light  crystalline  solid, 
with  the  formula  MgS04.7H20.     It   is   somewhat   efflo- 
rescent.    The  use  of  the  salt  in  medicine  as  a  purgative 
is  well  known.     It  is  also  sometimes  used  in  weighting 
cotton  goods.    Magnesium  carbonate  as  prepared  in  the 
laboratory  is  a  basic  salt,  having  the  formula  MgC03. 
Mg(HO)2.      This    is   because    of    the    hydrolysis   which 
takes  place.     It  is  a  fine,  white  powder  often  used  in 
tooth    pastes    and    in    metal    polishes.      The    chloride, 
MgCl2,  has  been  mentioned  as  a  deliquescent  salt,  found 
in  sea  water,  causing  the  dampness  often  observed  in 
table  salt. 

7.  Occurrence  of  Zinc. — The   greater  portion  of  the 
supply  of  zinc  in  the  United  States  is   obtained  from 
the  Joplin  district,  which  includes  not  only  southwest 
Missouri,  but  southeast  Kansas  and  northeast  Oklahoma. 
It  occurs  in  this  section  as  a  sulphide,  ZnS,  known  locally 
by  the  name  of  "jack"  but  scientifically  as  sphalerite 
or  zinc  blende.    In  some  parts  of  the  district  it  is  mixed 
'with  a  lead  ore,  galena,  also  a  sulphide.     In  several  of 
the   Western   States,  for  example,   Colorado   and  Mon- 
tana,  zinc   occurs  mixed  with   copper  and   silver  ores, 
usually  as  a  sulphide ;  in  some  of  the  Eastern  States  it 
occurs  as  franldinite,  ZnO.Fe203. 

8.  Reduction   of  Zinc   Ores. — Several   of   the   metals 
thus  far  studied,  notably  the  silver  group,   are  either 
found  free  or  may  be  reduced  by  heat  alone.     Some  of 
the  copper  ores,  because  of  their  complexity  and  mixture 
of   other   metals,    require    special   treatment,    but    even 


THE    MAGNESIUM   FAMILY  383 

many  of  these  may  be  reduced  by  heat  alone.  Most  of 
the  other  metals  studied  thus  far  are  reduced  electro- 
lytically.  Zinc  introduces  a  third  type,  those  which  re- 
quire the  aid  of  some  reducing  agent,  such  as  carbon. 
The  process  will  be  considered  very  briefly.  As  carbon, 
even  when  heated,  does  not  combine  readily  with  sul- 
phur, it  becomes  necessar}^  to  convert  the  zinc  ores  into 
an  oxide.  This  is  done  by  a  process  known  technically  as 
"roasting."  The  term  means  heating  strongly  with  a 
plentiful  supply  of  air.  By  this  process  the  sulphur  and 
zinc  both  are  converted  into  oxides,  thus, 

2ZnS  +  302  -»  2S02  +  2ZiiO. 

The  zinc  oxide  is  next  mixed  with  coke,  heated  strongly 
in  cylindrical  retorts  made  of  fire  clay.  The  zinc  dis- 
tils out  in  the  form  of  vapor  and  is  condensed. 

9.  Characteristics  of  Zinc. — Zinc  is  a  bluish-white 
metal  with  a  melting  point  of  about  420°  C.,  and  boiling 
point  of  950°  C.  It  will  be  seen  that  a  temperature  suffi- 
cient to  melt  silver  will  vaporize  zinc.  "Spelter,"  as 
the  product  from  the  zinc  smelters  is  called,  is  brittle ; 
but  if  heated,  at  a  temperature  between  125°  and  150° 
C.,  it  becomes  malleable.  Rolled  into  sheets  at  this 
temperature  its  malleability  becomes  permanent.  It  is 
a  poor  conductor  of  heat  and  electricity.  It  is  only 
slightly  attacked  by  the  air,  for  the  basic  carbonate 
w^hich  forms  upon  the  surface  is  closely  adhering  and 
protects  the  metal  almost  as  if  painted.  AVater  is  not 
decomposed  by  zinc,  but  dilute  acids  are  readily,  with 
the  evolution  of  hydrogen.  This  is  especially  true  of 
commercial  zinc  which  is  somewhat  impure.  Molten  zinc 
mixes  readily  with  silver,  copper,  tin  and  antimony, 
but  not  with  lead  or  bismuth.  Melted  with  lead  it  will 
float  as  ether  upon  water  with  only  a  small  quantity 
of  each  dissolved  in  the  other.  This  fact  is  employed 


384  APPLIED 

in  separating  silver  from  lead  when  obtained  from  ar- 
gentiferous lead  ores. 

10.  Uses. — Because  of  its  nonconductivity  it  is  often 
used   for   lining   refrigerators    and   beneath    or   behind 
stoves  to  protect  the  floors  or  walls.    Its  most  extensive 
use,  probably,  is  for  "galvanizing"  iron.     This  is  not 
done  electrolytically  as  the  name  might  imply,  but  by 
dipping  the  heated  iron,  previously  well  cleaned,  into 
molten  zinc.     Upon  withdrawing  the  iron  a  coating  of 
zinc  adheres.     Practically  all  iron  wire  fencing  is  now 
made  in  this  way.      Galvanized  sheet  iron  is  used  for 
gutters,    downspouts,    cornice    work,    granaries,    wind 
mills,  feed  and  watering  troughs,  as  well  as  for  countless 
smaller  articles.     Dry  cells  consist  of  a  container  made 
of  zinc  which  serves  as  the  positive  plate,  a  carbon  rod 
at  the  center  as  the  negative,  and  a  packing,  in  part, 
of  sal  ammoniac  or  some  other  salt  which  reacts  with 
the   zinc.     Many  valuable  alloys   of  zinc   are   familiar. 
Brass  and  German  silver  have  already  been  mentioned. 
Some  "white"  metals,  from  which  various  articles  of 
plated  silverware  are  made,  are  an  alloy  of  copper  and 
zinc  in  which  the  proportion  of  zinc  is  high,  to  such  an 
extent  that  the  color  of  the  copper  is  not  apparent  at  all. 

11.  Zinc   Sulphate,    ZnS04.7H20.— Commercially   this 
compound  is  known  under  the  name  of  white  vitriol.   It 
contains  the  same  quantity  of  combined  water  per  mole- 
cule as  magnesium  sulphate.     It  may  be  prepared  by 
treating  zinc  with  dilute  sulphuric  acid  or  from  the  native 
blende  in  a  similar  manner.    Like  magnesium  sulphate  it 
is  efflorescent.    It  is  used  somewhat  as  a  mordant  and  to 
some  extent  as  an  antiseptic  in  medicine.     A  mordant  is 
a  reagent  which  has  the  power  of  fixing  a  dye  in  the  fibers 
of  a  cloth  so  that  it  is  not  easily  removed  by  water. 


THE    MAGNESIUM    FAMILY  385 

12.  Zinc  Chloride,  ZnCl2. — This  is  a  white  compound 
which   may  be  prepared  by   treating   zinc  with   dilute 
hydrochloric  acid  in  slight  excess  and  boiling  to  dry- 
ness.     It  is  very  deliquescent  and  in  solution  gives  an 
acid  reaction  owing  to  partial  hydrolysis.    For  this  rea- 
son it  is  commonly  used  in  soldering  as  a  flux  to  give 
a  clean  surface.    The  free  hydrochloric  acid  in  the  solu- 
tion dissolves  the  film  of  oxide  always  present,  so  that  the 
melted  solder  may  come  into  direct  contact  with  the  metal. 
Melted  zinc  chloride  has  the  remarkable  property  of  be- 
ing able  to  dissolve  cellulose ;  by  dipping  sheets  of  paper 
into  the  liquid,  parchment  is  made. 

13.  Zinc  Oxide,  ZnO. — As  usually  obtained,  zinc  oxide 
is  a  faintly  yellow  compound.    Perfectly  pure  it  is  white 
when  cold,  but  distinctly  yellow  when  hot.    It  is  a  valua- 
ble by-product  of  many  smelters,  being  obtained  by  the 
roasting  of  ores  containing  a  very  small  percentage  of 
zinc.     The  oxide  is  vaporized  and  carried  over  with  the 
sulphur  dioxide  and   other  gases  and  is   condensed  in 
large,  cool  chambers  upon  coarse  sacking.     Afterward 
it  is  purified  by  continued  heating  below  its  point  of 
vaporization.    It  is  used  extensively  in  the  manufacture 
of  paints  and  enamels.     Ground   in   oil   the  former   is 
sold   under   the   trade   name   of   "zinc   white."      Small 
quantities  of  the  oxide,  carefully  purified,  are  used  in 
pharmacy  for  making  salves  and  other  applications  for 
skin  diseases.     Its  action  is  probably  largely  antiseptic. 
It  is  also  used  in  dentistry  in  making  temporary  fill- 
ings for  teeth,  especially  for  children.    For  this  purpose 
it  is  mixed  with  glacial  phosphoric  acid  (p.  280)  to  form 
a  soft  mass  which  is  placed  in  the  prepared  cavity.     It 
very  soon  hardens  much  as  does  plaster  of  Paris,  form- 
ing an  oxyphosphate  of  zinc.     This  oxide  is  of  interest, 
for  the  reason  that  it  possesses  a  dual  character,  serv- 


386  APPLIED    CHEMISTRY 

ing  sometimes  as  if  basic  and  again  as  if  acidic.  In  the 
hydrated  form,  Zn(HO)2,  it  readily  dissolves  in  dilute 
acids,  forming  zinc  salts,  in  which  zinc  is  the  posi- 
tive ion.  On  the  other  hand,  it  will  dissolve,  though 
somewhat  less  readily,  in  strong  bases,  such  as  sodium 
hydroxide.  It  then  forms  salts  called  "zincates"  in 
which  zinc  is  found  in  the  negative  ion.  Thus, 

2HCl  +  Zn(HO)2  -»  ZnCl2  +  2H20, 
2NaHO  +  Zn(HO)2  -»  Na2ZnO2  +  2H20. 

In  these  cases  the  zinc  hydroxide  evidently  has  ionized 
as  follows, 

£n(HO)2  ±5  H2Zn02  *±  Zn  +  (HO)  (HO)  +  H,H  +  Zn62. 
Therefore,  although  zinc  hydroxide  is  but  slightly  solu- 
ble in  water,  such  portions  as  do  dissolve  are  evidently 
ionized  in  both  ways  in  fixed  definite  amounts.  From 
the  location  of  zinc  in  the  periodic  table,  not  far  from 
the  diagonal,  such  behavior  might  be  expected. 

14.  Occurrence  of  Mercury. — Mercury  has  been-  known 
at  least  since  300  B.C.  when  it  was  prepared  by  Theo- 
phrastus,  who  gave  it  the  name  meaning  liquid  silver. 
Its  symbol  is  derived  from  the  Greek  word,  hydrargyrum. 
It  is  found  in  comparatively  small  quantities  and  in  few 
places  in  the  world.     In  America  the  mines  in  central 
California  are  the  most  productive.     In  Europe,  Spain 
and  Austria  produce  the  greater  part.     In  all  cases  the 
sulphide,    HgS,    known   as    cinnabar,    with    some    inter- 
mingled free  mercury,  is  the  ore  found.     From  this  the 
mercury  is  obtained  by  distillation. 

15.  Characteristics  of  Mercury.— Mercury  is  the  only 
metal,  liquid  at  ordinary  temperatures.     It  becomes  a 
solid  at  about  -39°  C.  and  boils  about  360°.    In  the  solid 
form  mercury  is  somewhat  malleable  and  to  a  consid- 
erable  extent   resembles   lead.      It   dissolves    or   alloys 


THE    MAGNESIUM    FAMILY  387 

readily  with  many  of  the  other  metals,  especially  gold, 
silver,  copper,  tin  and  zinc.  Such  alloys  are  called  amal- 
gams. They  may  be  obtained  by  putting  the  finely  di- 
vided metals  into  mercury,  or  a  surface  amalgamation 
may  be  had  by  dipping  the  clean  metal  into  a  solution 
of  some  salt  of  mercury.  A  bit  of  clean  gold  dropped 
upon  mercury  will  sink  and  dissolve  as  a  lump  of  sugar 
in  a  cup  of  hot  water.  Again,  a  clean  penny  in  a  solu- 
tion of  mercuric  nitrate  soon  takes  on  a  coating  of  mer- 
cury which  upon  slight  rubbing  has  the  appearance  of 
burnished  silver.  In  the  latter  case  an  amount  of  cop- 
per has  dissolved  equivalent  to  the  mercury  deposited, 
that  is,  one  atomic  weight  of  copper  has  been  dissolved 
for  each  atomic  weight  of  mercury  deposited.  Mercury 
is  not  tarnished  by  the  air,  nor  does  it  set  free  hydrogen 
from  acids  It  decomposes  nitric  acid  and  boiling  sul- 
phuric with  the  usual  results  in  such  cases.  The  two 
equations  following  indicate  the  reactions, 

3Hg  +  8HN03  ->  3Hg(N03)2  +  4H20  +  2NO, 
Hg  +  2H2S04  -»  HgS04  +  2H20  +  S02. 
16.  Uses  of  Mercury. — The  use  of  mercury  for  amalga- 
mating copper  plates  and  otherwise  in  obtaining  gold  has 
been  described.  (See  p.  374.)  It  is  used  in  thermometers 
and  to  some  extent  in  barometers,  although  the  aneroid 
is  taking  the  place  of  the  mercurial  barometer  in  many 
places.  The  advantages  of  mercury  in  thermometers 
are  that  it  has  a  high  and  uniform  rate  of  expansion 
through  a  lone:  range  of  temperature  and  is  of  high 
boiling  point.  Alcohol  thermometers  are  valuable  for 
use  below  the  freezing  point  of  mercury.  Zinc  plates 
in  galvanic  batteries  are  commonly  amalgamated  to 
prevent  local  circuits  with  rapid  wasting  of  the  metal. 
In  dentistry  amalgam  fillings,  consisting  of  silver  and 
tin  with  sufficient  mercury  to  form  a  soft  pliable  mass, 


388  APPLIED    CHEMISTRY 

are  commonly  used  except  for  front  teeth.  This  amal- 
gam has  the  property  of  setting  rapidly  and  of  retaining 
its  color,  while  dental  amalgams  containing  cadmium, 
a  metal  formerly  used  considerably,  turn  dark  and  be- 
come unsightly. 

17.  Mercuric  Oxide,  HgO.— This  is  a  heavy  solid,  crys- 
talline  or  amorphous,  yellow,   orange  or  red  in  color, 
according  to  the  method  by  which  it  is  obtained.     The 
yellow  is  obtained  by  treating  a  warm  solution  of  mer- 
curic chloride  or  of  some  other  mercuric  salt  with  sodium 
or  potassium  hydroxide  solution,  in  slight  excess.     The 
hydroxide,  formed  at  first,  quickly  decomposes  into  mer- 
curic oxide  and  water,  thus,  , 

HgCl2  +  2KHO  -»  Hg(HO)2  +  2KC1-*  HgO  +  H20  +  2KC1. 

It  is  regarded  as  the  same  chemically  as  the  orange  or 
red  variety  but  in  a  finer  state  of  division,  since  by 
trituration  the  red  variety  changes  to  yellow.  It  is  used 
somewhat  in  medicine  in  the  form  of  salves,  mainly  on 
account  of  its  antiseptic  properties. 

18.  Mercurous  Chloride  or  Calomel,  Hg2Cl2. — This  is 
a  finely  divided  white  powder  used  in  medicine.     It  is 
easily  prepared  in  the  laboratory  by  treating  a  solution 
of  mercurous  nitrate  with  a  solution  of  common  salt  or 
hydrochloric  acid,  thus, 

Hg2(N03)2  +  2NaCl  -»  Hg2Cl2  +  2NaN03. 

As  it  is  insoluble  in  water  it  is  easily  separated  by  filtra- 
tion. On  a  large  scale  it  is  made  by  mixing  common 
salt,  mercury  and  mercuric  sulphate  intimately  and  dis- 
tilling. The  calomel  passes  over  as  a  vapor  and  is  con- 
densed. It  is  apt  to  contain  small  quantities  of  the  mer- 
curic chloride  and  should  be  freed  from  it  by  washing. 
Like  all  salts  of  mercury,  calomel  is  poisonous  and  all 
the  excretory  organs  are  thereby  stimulated  by  its  pres- 


THE    MAGNESIUM    FAMILY  389 

ence.  Being  an  unsaturated  compound  it  tends  to  take 
up  an  additional  negative  ion  and  form  the  mercuric 
salt.  Therein  lies  the  danger  of  its  use  in  medicine,  that 
of  causing  mercurial  poisoning  with  consequent  saliva- 
tion. With  the  hydrochloric  acid  present  in  the  stomach 
or  in  the  presence  of  acid  foods,  the  mercurous  molecule 
begins  to  change  into  the  mercuric  chloride  which  is  much 
more  soluble.  Its  action  then  upon  the  system  is  rapid, 
and  before  it  is  eliminated  the  salivary  glands  may  be 
affected,  followed  by  the  well-known  soreness  of  gums 
and  teeth.  Such  instances  are  not  common  now,  for  physi- 
cians, knowing  the  danger,  administer  the  calomel  mixed 
with  common  soda.  This  neutralizes  the  acid  in  the  stom- 
ach and  prevents  the  calomel  changing  to  the  soluble 
form.  Even  as  given  now,  however,  acid  foods  should  not 
be  used  at  the  same  time. 

19.  Mercuric    Chloride,    HgCl,. — This    is    commonly 
known  as  corrosive  sublimate.     It  is  prepared  by  sub- 
limating a  mixture  of  common  salt  and  mercuric  sul- 
phate.    It  is  highly  poisonous.     The  white   of  eggs  is 
regarded  as  the  best  antidote,  with  which  the  mercuric 
salt  forms  an  insoluble  mass.     Owing  to  its  poisonous 
properties  it  is  an  excellent  antiseptic  and  is  frequently 
used  for  sterilizing  surgical  instruments  and  upon  band- 
ages for  wounds.    Applied  in  this  way  it  is  not  poison- 
ous.   To  prevent  "scab,"  a  disease  which  causes  a  rough 
surface   upon   potatoes,   a    dilute   solution   of   corrosive 
sublimate  is  sometimes  used  in  which  the  seed  potatoes 
are  immersed  a  short  time  before  planting. 

20.  Mercuric  Sulphide,  HgS. — The  artificial  sulphide  is 
sold  under  the  name  vermilion.    It  is  a  brilliant  red  pow- 
der, used  as  a  pigment.     Prepared  in  the  laboratory  by 
adding  hydrogen  sulphide  to  a  solution  of  some  mercuric 
salt  it  is  a  black  powder.    The  reaction  is 

HgCl,  +  H,S  -*  HgS  +  2HC1. 


390  APPLIED    CHEMISTRY 

If  this  black  precipitate  is  sublimed,  it  changes  to  the  red 
variety. 

Exercises  for  Review 

1.  Name  the  metals  of  the  magnesium  group.     Where  are  they 
located  in  the  table?     What  is  their  valence? 

2.  Give  the  important  natural  compounds  of  magnesium.     What 
are  the  chief  uses  for  asbestos? 

3.  Give  the  characteristics  of  magnesium.     In  what  two  forms 
does  it  occur? 

4.  What   are  the  principal  uses   of  magnesium?     State   why   so 
used. 

o.  What  is  magnesia?     What  are  its  chief  uses? 

6.  Give  formulas  and   uses  for  the   sulphate   and  carbonate   of 
magnesium. 

7.  Name   the   important  ores  of   zinc.     Where   is   it   mostly   ob- 
tained in  the  United  States? 

8.  How  is  zinc  blende  reduced?     Name  two  other  methods  of  re- 
duction and  some  metal  obtained  each  way. 

9.  Give  the  most  important  characteristics  of  zinc. 

10.  What  is  galvanized  iron?     Its  important  uses? 

11.  How    is    zinc    sulphate    obtained?      Its    commercial    name? 
What  other  vitriols  have  been  studied? 

12.  What  is  a  mordant? 

13.  Give  method   of  making  zinc   chloride.     Name   some  impor- 
tant use. 

14.  What  is  the  source  of  the  commercial  supply  of  zinc  oxide? 
What  is  its  chief  use? 

15.  From  what  are  the  temporary  fillings  for  teeth  made? 

16.  Chemically,  what  point  of  interest  attaches  to  zinc  oxide? 
.17.  Why  will  zinc  oxide  dissolve  both  in  acids  and  bases? 

18.  What  is  the  only  ore  of  mercury?     Where  found? 

19.  Give    the    important    properties    of    mercury.      What    is    an 
amalgam?     How  may  amalgams  be  made?     Name   some  uses  for 
them. 

20.  Give  some  valuable  uses  for  mercury. 

21.  How  may  yellow  mercuric  oxide  be  obtained?     What  other 
varieties  occur?     Wherein  are  they  different? 

22.  What   is   calomel?     What   danger   attaches   to   its  use   as   a 
medicine? 


THE  MAGNESIUM  FAMILY  391 

2a.  What   is  corrosive   sublimate?     Why  so  called?     What   uses 
lias  it? 

21.  How  may  vermilion  be  made?     Of  what  use  is  it? 
125.  Complete    these    equations   and    state   what    process   is    repre- 
sented, 

Mg  +  O2  ->  , 

MgCO3  (heated)  —  »  , 

ZnO  +  C  ->  , 

Zn  +  HC1  -»  , 

ZnO  +  HC1  ->  , 

HgS  +  <>,-», 

Hga(NO3)2  +  NaCl  —  >  , 

HgSO4  +  NaCl  +  Hg  -*  , 

HgSO4  +  NaCl  -^  , 


.  —  In  the   above   equations  the   student   must   supply  coeffi- 
cients as  needed  for  proper  quantity  of  each  reagent. 


CHAPTER  XXXII 

THE  ALUMINUM  FAMILY 

Outline- 
Members  of  the  Group 
Compounds  of  Boron 
Aluminum 

(a)  Occurrence  in  Nature 

(b)  Precious  Stones 

(c)  Manufacture  of  Aluminum 

(d)  Characteristics 

(e)  Uses  . 
(/)  Alloys 
(g)  Alums 

(7i)   Aluminum  Hydroxide 

1.  Members  of  the  Group. — Aluminum  is  the  only  im- 
portant metal  of  the  family.     Boron  is  a  member  and 
the  lightest  with  an  atomic  weight  of  only  11.    It  forms 
two  compounds  of  some   importance,   borax  and  boric 
acid.      The  former  has  been  studied  under  the  sodium 
compounds.     Boric   acid   is   a   white,   crystalline    solid, 
mildly  antiseptic,  and  frequently  used  in  solution  as  an 
eye  wash. 

2.  Abundance  of  Aluminum. — By  referring  to  Fig.  9 
on  p.  52  it  will  be  seen  that  aluminum  constitutes  about 
8  per  cent  of  all  the  matter  of  the  earth,  and  ranks  next 
to  silicon  in  abundance.    It  is  a  constituent  of  all  clays 
and  of  the  feldspar  rocks  from  which  clays  are  derived 
by  decomposition.    Mica,  a  rock  which  easily  splits  into 
thin  leaves  used  in  stoves  and  for  insulation  in  various 
ways,  is  a  silicate  of  aluminum  and  potassium.    Kaolin, 
Fuller's    earth,    garnets,    sapphires,    emeralds,    rubies, 
are  all  aluminum  compounds. 

392 


THE    ALUMINUM    FAMILY  393 

Corundum,  an  impure  oxide  of  aluminum,  ranks  next 
to  the  diamond  in  the  scale  of  hardness.  Emery  is  of 
the  same  composition  and  is  familiar  to  all.  It  is  used 
in  various  forms  as  an  abrasive:  emery  powder,  grind- 
stones, and  emery  wheels,  whetstones,  emery  paper  and 
emery  cloth.  Kaolin  is  a  pure  white  clay  used  in  making 
porcelain  ware  and  the  various  grades  of  china.  Ful- 
ler's earth  is  a  similar  compound  used  in  absorbing  the 
coloring  matter  from  vegetable  oils  such  as  that  made 
from  cotton  seed.  It  also  has  various  other  uses. 

3.  The  Precious  Stones. — To  the  mineralogist,  rubies, 
sapphires  and  emeralds  are  all  sapphires.    They  are  crys- 
tallized aluminum  oxide,  ALC^,  and  differ  from  emery 
in  that  it  is  uncrystallized  and  less  pure.     Their  color  is 
due  to  small  quantities  of  another  metallic  oxide.     At 
the  present  time  great  quantities  of  these  jewels  are  being 
manufactured  even  more  perfect  than  the  natural  stones 
and  with  all  their  characteristics.     The  white  sapphire, 
which  resembles  the  diamond  somewhat  though  less  bril- 
liant, is  of  the  same  composition  as  the  other  sapphires, 
but  uncolored.     These  stones  are  sometimes  spoken  of  as 
synthetic.     For   some   years,   it   is   said,   over   nine   mil- 
lion carats  of  rubies  and  about  half  as  many  sapphires 
have  been  made  annually.    The  garnet  is  more  complex  in 
composition  than  the  above  stones  being  an  orthosilicate 
of  aluminum  and  calcium,  Ca.5Al.,(Si04)3. 

4.  Preparation  of  Aluminum. — At  the  present  time  alu- 
minum is  made  by  the  electrolysis  of  bauxite,  a  hydrated 
oxide  of  aluminum.    The  principle  is  the  same  as  used  for 
sodium,  calcium  and  several  other  metals  already  studied. 
Bauxite,  however,   does  not  melt  easily,  neither  does  it 
dissolve  in  water.     The  problem,  therefore,  is  to  secure 
it  in  liquid  form  so  that  it  may  become  a  conductor.    An- 
other compound  of  aluminum  known  as  cryolite,  a  word 


394 


APPLIED    CHEMISTRY 


which  means  ice  stone,  and  given  to  this  mineral  because 
of  its  low  melting  point,  is  put  into  an  electric  furnace  and 
melted.  Powdered  bauxite  is  added  and  dissolves  read- 
ily. It  will  be  seen  that  the  cryolite  is  simply  a  solvent 
or,  as  it  is  technically  called,  a  flux.  When  the  current  is 
passed  the  bauxite  decomposes  and  the  aluminum  collects 
at  the  cathode.  Fig.  65  illustrates  the  process.  Fresh 
quantities  of  bauxite  are  added  from  time  to  time  as 
needed,  the  aluminum  is  drawn  off  occasionally  and  the 
process  is  continuous.  The  heat  generated  by  the  re- 
sistance to  the  current  keeps  the  cryolite  melted.  The 
manufacture  of  aluminum  is  carried  on  where  cheap 


Fig.   65. — Manufacture   of  aluminum. 

electric  power  may  be  had,  especially  at  Niagara  Falls. 
Up  to  the  present  time  no  commercial  method  has  been 
devised  for  extracting  aluminum  from  such  complicated 
compounds  as  clays.  Such  a  process  would  be  eminently 
desirable. 

5.  Characteristics  of  Aluminum.— Aluminum  is  a  white 
metal,  of  low  specific  gravity,  being  only  2.6  times  as 
heavy  as  water.  It  is  an  excellent  conductor  both  of 
heat  and  electricity.  As  a  given  weight  of  aluminum 
will  make  a  wire  of  much  greater  cross  section  than  the 
same  weight  of  copper,  it  is  even  better  than  copper  as 
a  conductor.  In  tensile  strength  it  is  not  greatly  dif- 
ferent from  copper  and  most  other  common  metals,  ex- 


THE    ALUMINUM    FAMILY  395 

cept  steel,  but  it  has  a  tendency  to  crystallize  and  un- 
protected wires  to  become  somewhat  brittle.  Its  melting 
point  is  about  700°  0.  At  ordinary  temperatures  it  does 
not  react  appreciably  with  oxygen  and  does  not  tarnish 
greatly  in  the  air.  It  is  ductile  and  malleable  and  easily 
made  into  thin  foil.  While  it  is  below  magnesium  in  the 
electromotive  series  of  metals,  it  is  strongly  positive. 
It  decomposes  concentrated  hydrochloric  acid  vigor- 
ously, with  the  evolution  of  hydrogen.  With  nitric  acid 
the  action  is  practically  nil;  with  sulphuric  acid  there  is 


Fig.    66. — Thermit    crucible,    sectional    view. 

practically  no  action  at  room  temperature,  but  when 
heated  to  boiling  the  metal  is  oxidized  and  sulphur  di- 
oxide evolved  as  is  usual  in  such  cases.  Strong  alkaline 
solutions  attack  aluminum  readily  and  form  a  class 
of  salts  called  aluminates,  corresponding  to  the  zincates, 
mentioned  previously. 

6.  Uses.- — On  account  of  its  electric  conductivity  it  is 
used  in  some  localities  as  feed  wires  for  trolley  systems. 
In  the  home  it  makes  an  ideal  cooking  vessel.  Its  con- 
ductivity is  about  the  equal  of  copper,  so  that  all  por- 
tions of  the  vessel  become  heated  alike  and  food  prod- 
ucts which  burn  easily  are  much  less  readilv  scorched 


396 


APPLIED    CHEMISTRY 


than  in  ordinary  granite  ware  or  tinware.  Further,  it 
is  not  attacked  by  weak  acids  such  as  those  found  in 
any  fruits  used  as  food.  Moreover,  it  is  light,  does  not 
tarnish  readily,  and  is  easily  cleaned.  Anything  alkaline 


Fig.    67. — A    thermit    crucible    ready    for    use    in    mending    a    broken    casting. 
(By  courtesy  of  the   Goldschmidt  Thermit   Co.) 

in  character  cannot  be  cooked  in  aluminum  vessels  but 
none  of  our  food  is  alkaline.  In  the  finely  powdered 
form  aluminum  is  mixed  with  linseed  oil  and  used  as  a 
paint  for  metallic  objects  to  which  it  adheres  well.  Its 
use  in  this  way  is  seen  in  many  of  the  penny-weighing 


THE    ALUMINUM    FAMILY 


397 


machines,  mail  boxes,  steam  and  hot  water  radiators, 
and  other  familiar  objects.  Very  considerable  quanti- 
ties of  powdered  aluminum  are  used  in  a  patented  arti- 
cle called  "thermit."  This  consists  of  ferric  oxide  and 


Fig.    68. — A   thermit    crucible    in    operation,    mending   a    broken    casting.      (Hy 
courtesy    of   the    Goldschmidt    Thermit    Co.) 

aluminum  intimately  mixed;  for  use  it  is  put  into  a  cru- 
cible of  suitable  size,  conical  in  shape,  as  shown  in  Fig. 
66,  and  a  small  amount  of  powdered  magnesium  placed 
on  top  as  kindling.  When  eve^thing  is  ready  the  mag- 
nesium is  lighted.  The  heat  thus  obtained  is  sufficient 


398  APPLIED    CHEMISTRY 

to  start  the  chemical  action  between  the  aluminum  and 
ferric  oxide,  Fe203.  Once  begun  it  is  self  continuous 
from  the  heat  liberated'.  In  a  short  time  the  aluminum 
has  become  aluminum  oxide  and  the  iron  is  free,  in  a  mol- 
t?n  condition  with  a  temperature  over  1,500°.  In  fact, 
it  is  said  that  a  temperature  of  3,000°  is  often  reached 
in"  the  process.  By  substituting  the  oxides  of  other 
metals,  such  as  chromium  or  vanadium  or  manganese,  it 
is  possible  to  obtain  these  rare  metals  in  a  pure  condition. 
The  process  is  used  for  welding  almost  everything  of 
any  size,  made  of  iron  or  steel.  Thus  are  mended  broken 
drive  wheels  for  locomotives,  propeller  shafts  for  great 
engines,  rails  in  street  railway  systems,  and  the  like. 
It  is  frequently  used  on  shipboard  for  repairs  not  easily 
made  otherwise.  The  aluminum  oxide  obtained  as  a  by- 
product, is  often  used  for  the  manufacture  of  synthetic 
rubies  and  sapphires  already  mentioned  and  as  an  abra- 
sive. Another  extensive  use  for  aluminum  is  in  the  man- 
ufacture of  steel.  There  is  a  tendency  for  molten  steel, 
made  as  much  of  it  is,  to  retain  oxygen  or  other  gases 
within  the  mass.  This  is  probably  due  to  the  viscosity. 
When  such  ingots  of  steel  are  made  into  rails  these  "air 
holes"  form  weak  places  and  probably  are  occasionally 
the  cause  of  railway  accidents.  On  account  of  the  ten- 
dency of  aluminum  to  combine  with  oxygen  readily 
at  high  temperatures,  a  certain  amount  of  the  metal  is 
added  to  the  steel:  the  aluminum  combines  with  the  oxy- 
gen, forms  a  kind  of  slag  and  rises  to  the  top. 

7.  Alloys. — Aluminum  forms  several  alloys  of  value. 
Magnalium,  containing  about  2  per  cent  of  magnesium, 
has  already  been  mentioned.  (See  p.  381.)  Aluminum 
bronze  is  prepared  in  two  varieties,  one  with  a  very 
small  percentage  of  copper,  which  is  even  whiter  than 
pure  aluminum  and  resembles  silver  .  closely  except  in 


THE    ALUMINUM    FAMILY  399 

density.  It  is  used  extensively  in  novelty  articles  and 
occasionally  in  such  kitchen  utensils  as  teapots.  The 
other  variety,  with  copper  as  high  as  90  per  cent,  some- 
what resembles  gold  in  color  and  is  frequently  used  in 
making  Avatch  cases  as  well  as  a  great  variety  of  novelty 
articles. 

8.  Alums. — An  alum  is  a  double  sulphate  of  a  univalent 
and   a  trivalent  metal.     There   are  many  of   them,   but 
the    most    common    is    potassium    aluminum     sulphate, 
K2S04.A12(S04)3.24H20.     Almost  as   common  is  ammo- 
nium alum  in  which  ammonium  has  taken  the  place  of  the 
potassium  in  common  alum.    Sodium  being  univalent,  en- 
ters into  the  composition  of  several  alums;   chromium 
and  trivalent  iron,  likewise,  may  take  the  place  of  alu- 
minum in  common  alum.    They  are  all  hydrates  and  con- 
tain the  same  amount  of  water;  they  are  all  also  iso- 
morphous,  that  is,  they  all  crystallize  in  the  same  shape. 
"Burnt"  alum  is  obtained  by  heating  alum  to  expel  the 
water  of  combination.    It  is  a  mild  caustic  and  is  some- 
times used  medicinally  in  that  way,  especially  for  ulcer- 
ations  of  the  mouth. 

9.  Uses  of  Alum. — Mention  has  already  been  made  that 
alum  is  used  as  a  coagulant  in  purifying  muddy  waters 
for  city  supplies.     More  often,  not  alum,  but  aluminum 
sulphate  is  used,  although  it  is  generally  referred  to  as 
alum.     Its  reaction  with  the  milk  of  lime  is 

3Ca(HO)2  +  A12(S04)5  -»  A1,(HO)6  +  3CaS04. 
Likewise,  alum  has  been  spoken  of  as  an  ingredient  of 
baking  powders.  More  often,  here  also,  aluminum  sul- 
phate is  used  instead  of  real  alum.  It  is  supplied  the 
baking  powder  factories  under  the  trade  name  of  C.T.S. 
meaning  "cream  tartar  substitute."  The  chemical  action 
has  already  been  noted  on  page  329. 

10.  Aluminum  Hydroxide,   Al,(HO)(i. — This  is  easily 


400  APPLIED    CHEMISTRY 

prepared  in  the  laboratory  by  treating  a  solution  of 
alum  with  ammonium  or  sodium  hydroxide,  taking  care 
not  to  use  the  latter  reagent  in  excess.  Sodium  carbon- 
ate may  be  substituted  for  the  alkali.  It  is  a  white 
gelatinous  precipitate,  in  many  ways  a  very  interesting 
compound  chemically.  Like  zinc  hydroxide,  it  ionizes 
both  as  a  base  and  as  an  acid,  thus. 

-H-+ 

A1(HO)3^±A1+  (HO),   (HO),   (HO), 
H8A10a  *=±  H,  H,  H  +  Al"<58. 

As  a  result  aluminum  hydroxide  is  very  soluble  not  only 
in  acids,  with  which  it  forms  aluminum  salts  with  alu- 
minum as  the  positive  ion,  but  is  also  soluble  in  bases, 
with  which  it  forms  aluminates,  in  which  the  negative  ion 
is  -A1O3.  To  illustrate, 

A1(HO)3  +  3HC1  ->  A1C13  +  3H2O, 
H8A103  +  3NaHO  -»  Na3A103  +  3H20. 

Its  position  in  the  table,  near  the  acid  forming  elements, 
would  lead  us  to  expect  such  behavior. 

On  account  of  its  gelatinous  character  not  only  has  it 
the  power  of  clarifying  muddy  waters,  but  also  of  remov- 
ing colors  from  solutions.  Thus,  if  an  alum  solution, 
deeply  colored  with  some  dye,  such  as  carmine,  has  a 
little  alkali  added  to  precipitate  the  aluminum  as  hydrox- 
ide, in  settling,  the  aluminum  hydroxide  will  carry  with 
it  practically  all  the  coloring  matter.  Such  precipitates 
dried  and  ground  in  oil  are  sold  as  tube  paints  for  artists 
under  the  name  of  lakes,  of  crimson  and  other  brilliant 
colors.  It  is  the  same  principle  that  makes  it  a  good  mor- 
dant. Precipitated  within  the  fibers  of  the  cloth  it  holds 
or  fixes  the  color.  Canvas  for  tents  and  other  fabrics 
are  sometimes  waterproofed  by  this  compound.  Treated 
first  with  aluminum  chloride  or  some  similar  compound 


THE    ALUMINUM   FAMILY  401 

the  cloth  is  heated  by  steam  which  hydrolyzes  the  alu- 
minum compound,  forming  aluminum  hydroxide  within 
fibers  of  the  cloth.  Upon  drying  it  becomes  waterproof. 
Some  papers  are  sized  by  aluminum  hydroxide.  To  the 
pulp  aluminum  sulphate  and  rosin  soap  are  added ; 
through  hydrolysis  aluminum  hydroxide  is  precipitated 
in  the  pulp.  When  dry  it  is  run  between  hot  rollers. 
This  melts  the  rosin  and  gives  a  surface  to  the  paper  while 
the  aluminum  hydroxide  fills  the  pores,  so  that  ink  is  not 
taken  up  readily. 

Exercises  for  Keview 

1.  Name  the  members  of  the  aluminum  family  and  give  location 
in  the  table. 

2.  State   Avhat  is  true   of  the   abundance   of  aluminum.     Name 
some  familiar  natural  compounds. 

3.  What  is  emery?     The  ruby?     Kaolin?     A  synthetic  stone? 

4.  Describe  the  preparation  of  aluminum.     What  is  a  flux? 

5.  Give  the  characteristics  of  aluminum. 

6.  Why  is  aluminum   suited  for  cooking  vessels?     What  advan- 
tage has  it  over  copper? 

7.  Describe  the  use  of  thermit. 

8.  Name  some  alloys  of  aluminum  and  give  uses. 

9.  What  is  an  alum?     Name  two.     What  is  burnt  alum? 

10.  What  is  the  meaning  of  the  term  isomorphous? 

11.  Why  is  aluminum  hydroxide  soluble  in  both  acids  and  bases? 
What  other  hydroxide  has  been  seen  to  have  the  same  property? 

12.  How  are  painters'  lakes  made? 

13.  What  is  meant  by  sizing  paper? 

14.  Complete  the  following  equations, 

Al,(S04)3  +  KHO  -»  , 
A1,(HO)6  +  H2S04  -»  , 
A1,(HO)B  (heated)  ->  , 
A12O3   (electrolysed)   — »  , 
Fe2O3  +  Al  — »  , 
Al   h  O2  -^  . 

Note. — The  student  will  use  the  amounts  as  needed  in  the  above 
equations. 


CHAPTER  XXXIII 

THE  LEAD  FAMILY 
Outline — 

Members  of  the  Group 
Tin 

(«)   Occurrence 

(b)  Characteristics 

(c)  Uses 

(d)  Alloys 

(e)  Compounds 
Lead 

(a)  Occurrence 

(b)  Characteristics 

(c)  Uses 
(of)   Alloys 

(e]   Compounds 

(a)  The  Oxides 

(b)  Lead  Acetate 

(c)  White  Lead 

(d)  Chrome  Yellow 
Storage  Batteries 

1.  Metals  of  the  Group. — The  only  common  metals  be- 
longing to  this  group  are  tin  and  lead,  the  former  with 
an  atomic  weight  of  119  and  the  latter,  207.1.     Their 
position  in  the  table  should  show  a  valence  of  four  and 
their  higher  oxides  indicate  this. 

2.  Occurrence  of  Tin. — The   oldest  tin  mines  of  the 
world  are  those  of  Cornwall,  England.     It  is  said  that 
the   ancient   Phoenicians   obtained   their   supplies   from 
this  source.     These  mines  now  at  great  depth  and  ex- 
tending out  under  the  ocean  are  still  in  operation  but 
produce  scarcely  10  per  cent  of  the  world's  output  of 
the  present  time.     Most  of  that  used  comes  from  the 

402 


THE    LEAD    FAMILY  403 

East  Indies  where  it  is  found  as  tin  oxide,  Sn(X,  called 
cassiterite.  It  is  the  same  ore  as  that  from  the  English 
mines. 

3.  Characteristics. — Tin  is  a  white  metal  with  a  melt- 
ing point  of  232°  C.    It  is  soft,  very  malleable  and  has  a 
specific   gravity  of  7.3.     It   is   crystalline   in  structure, 
but  much  less  so  than  antimony  or  bismuth.     Like  phos- 
phorus, sulphur  and  some  other  elements  already  stud- 
ied, tin  also  occurs  in  an  allotropic  form  not  often  seen. 
Kept  continuously  below  20°  C.  it  sometimes  changes  to 
a  gray  powder,  expanding  to  such  an  extent  that  its 
specific  gravity  is  only  5.8.     Tin  is  not  tarnished  in  the 
air  or  attacked  by  any  of  the  organic  acids.     It  decom- 
poses hydrochloric  acid  with  the  evolution  of  hydrogen, 
also  concentrated  nitric,  with  the  formation  of  nitrogen 
peroxide.    Hot  sulphuric  acid  gives  off  with  tin  sulphur 
dioxide,  as  is  usual  in  such  cases. 

4.  Uses   of  Tin. — Because   of  its  permanence   in  the 
air  tin  is  used  extensively  in  protecting  iron  in  what 
is  called  "tin  plate."     It  is  made  in  a  manner  similar 
to  that  used  for  galvanizing  iron.     Clean,  heated  sheets 
of  steel  are  dipped  into  molten  tin  and  upon  removal  a 
coating  adheres.     However,  as  iron  is  more  electroposi- 
tive than  tin,  if  the  coating  is  scratched  so  as  to  expose 
the  iron  the  corrosion  is  then  rapid.    The  reverse  is  true 
with  galvanized  iron.    Of  tin  plate  are  made  the  so-called 
"tin  cans"  used  so   extensively  in  preserving  various 
food  products.    During  the  year  1919  more  than  six  bil- 
lion  tin   cans   were   used   in   the   United   States   in   the 
various  canned-food  industries.     In  the  infancy  of  food 
preservation  in  this  manner,   each  canner  made  in  his 
own  establishment  by  hand  labor  the  cans  needed.     A 
good  workman  could   not  produce   over   150  per   day; 
now  by  machine  they  are  turned  out  at  the  rate  of  about 


404  APPLIED    CHEMISTRY 

one  per  second.  Heavy  tin  plate  is  used  for  roofing 
and  gutters.  Some  years  ago  cooking  vessels  of  tin 
plate  were  common,  but  they  have  been  largely  replaced 
by  granite  ware,  which  is  more  serviceable,  and  more 
recently  by  aluminum.  Copper  cooking  vessels  used  in 
large  eating  houses,  such  as  the  Harvey  system,  are 
tinned  on  the  inside  to  prevent  attack  by  organic  acids. 
This  has  to  be  done  somewhat  frequently,  but  the  proc- 
ess is  simple.  The  vessel  is  thoroughly  cleaned  as  if 
for  soldering,  is  heated  to  the  melting  point  of  tin  and 
then  the  powdered  metal  rubbed  on  the  surface  to  which 
it  adheres.  The  flux  used  in  cleaning  the  copper,  usu- 
ally ammonium  chloride,  prevents  oxidation  when  the  ves- 
sel is  heated.  Common  brass  pins  usually  have  a  thin 
coating  of  tin  to  prevent  their  tarnishing  in  the  air. 

5.  Alloys. — Many  valuable  alloys  of  tin  are  used  in 
the  arts.     Bronze  is  composed  of  copper  and  tin,  some- 
times with  zinc  added;  brittania  and  pewter  have  al- 
ready been  mentioned,  as  have  certain  fusible   alloys. 
(See  p.  289.) 

Soft  solder  contains  tin  and  lead  in  equal  proportions. 
Tin  is  also  an  important  component  of  the  most  common 
dental  amalgams. 

6.  Compounds. — Tin  forms  both  stannous  and  stannic 
salts,  represented  by  the  chlorides,  SnCl2  and  SnCl4.   The 
stannous    chloride    is    an    unsaturated    compound    and 
therefore   a   reducing   agent.     Added  to   a   solution   of 
mercuric  chloride,  first  a  white  precipitate  of  calomel 
is   obtained;   upon  warming   or   adding  more   stannous 
chloride  a  gray  or  black  precipitate  is  formed  consisting 
of  finely  divided  mercury  or  a  mixture  of  it  with  mer- 
curous  chloride.     These  two  equations  represent  the  re- 
actions occurring, 


THE    LEAD    FAMILY  405 

2HgCla  +  SnCL  -»  SnCl4  +  IIg2CL, 
Hg2Cl2  -f  SnCl2  ->  SnCl4  +  2Hg. 

The  experiment  serves  as  a  test  for  mercuric  compounds, 
or  reversed,  for  a  stannous  salt.  On  account  of  this 
reducing-  power  of  stannous  chloride  it  is  used  with 
"•old  chloride  in  toning  printing  out  papers  as  already 
described. 

There  are  two  oxides  of  tin,  stannous,  SnO,  and  stan- 
nic, Sn02.  The  latter  is  the  compound  found  native. 
It  may  be  obtained  by  treating  tin  with  concentrated 
nitric  acid  and  heating  the  white  powder  obtained.  It 
is  white  when  cold,  but  distinctly  yellow  when  hot. 
Stannic  acid,  which  is  a  white  gelatinous  compound, 
is  used  extensively  in  weighting  silk  goods.  The  chlo- 
rides are  used  somewhat  as  mordants. 

7.  Occurrence  of  Lead.— Galena,  PbS,  is  the  only  im- 
portant ore  of  lead.     It  is  a  lustrous,  dark  gray  mineral 
crystallizing  in   cubes,   with   cubical   lines   of   cleavage. 
It  is  associated  with  many  of  the  zinc  deposits  in  south- 
west Missouri  and  with  silver  and  other  metals  in  many 
of  the  Western  States. 

8.  Characteristics  of  Lead. — Lead  is  a  dark  gray  metal 
with  a  specific  gravity  of  11.38;  it  is  soft  and  malleable 
but   of  little   tenacity.     It   tarnishes   somewhat   readily 
in  the  air,  but  the  coating  adheres  firmly  and  serves 
to  protect  the  metal  from  further  oxidation.     The  melt- 
ing point  is  325°  C.    Being  just  above  hydrogen  in  the  elec- 
tromotive  series  it   has  little   power  of  replacing   that 
element  in  acids.     With  nitric  acid  it  reacts  as  do  most 
of  the  metals  to  form  nitric  oxide,  thus, 

3Pb  +  8HNO.,  -*  3Pb(N(X)2  +  4H20  +  2NO. 

Sulphuric  acid,  boiling  hot  and  much  concentrated  pro- 
duces sulphur  dioxide,  thus, 


406  APPLIED    CHEMISTRY 

Pb  +  2H2S04  ->  PbS04  +  2H20  +  S02. 

Acetic  acid,  though  a  weak  organic  acid,  reacts  slowly 
with  lead,  forming  the  acetate.  Lead  salts  are  all  poi- 
sonous and  are  difficult  of  elimination  from  the  system, 
hence  are  what  are  called  accumulative  poisons. 

10.  Uses. — Lead  is  used  largely  for  making  pipe.   Mol- 
ten lead  near  the  point  of  solidification  is  forced  by  hy- 
draulic pressure  through  annular  openings.     It  is  used 
as  waste  pipes  in  plumbing,  and  for  protecting  over- 
head and  underground  electric  cables.     In  sheet  form 
lead  is  used  to  line  the  rooms  where  chamber  sulphuric 
acid  is  manufactured,  also  for  sinks  in  chemical  laborato- 
ries and  other  places  where  acids  are  used.     Many  of 
its  alloys  are  valuable.     Common  solder  has  been  men- 
tioned as  has  also  type  metal,  containing  lead,  antimony 
and  tin.     It  will  also  be  recalled  that  shot  is  an  alloy 
of  lead  and  arsenic.     Alloyed  with  antimony  it  is  used 
extensively  in  making  storage  batteries. 

11.  The  Oxides. — Three  oxides  of  lead  are  common, 
the  monoxide,  PbO,  often  called  litharge;  lead  dioxide, 
PbO2 ;  and  minium,  Pb304,  often  called  red  lead.     The 
first  is   of  light  brown  color,   the   second   dark   brown 
and  the  third  red.     All  are  in  the   form   of   powders. 
Litharge  is  a  by-product  of  the  silver  refineries  and  is 
used  largely  in  the  manufacture  of  flint  glass.     (See  p. 
300.)      Red  lead  is  used  in  making  gas-tight   joints   in 
plumbing,  also  as  a  red  paint  for  metals.    The  dioxide  is 
used  in  storage  batteries. 

12.  Lead  Acetate,   Pb(C2H,02)2.3H20.— Commercially 
this  is  known  as  sugar  of  lead  because  of  its  sweet  taste. 
It  is  easiest  made  by  treating  lead  monoxide  with  acetic 
acid,  thus, 

2HC2H302  -»  H20  +  Pb(C2H302)2. 


THE    LEAD    FAMILY  407 

It  is  a  white  crystalline  salt,  readily  soluble  in  water. 
It  is  often  used  in  solution  as  an  external  application 
in  cases  of  "ivy  poisoning." 

13.  White  Lead. — Chemically,  white  lead  is  basic  lead 
carbonate,  Pb(HO)2.2PbC03.  It  is  the  most  commonly 
used  white  paint.  It  was  formerly  made  entirely  by 
what  was  known  as  the  "old  Dutch  process"  which  re- 
quired several  weeks  for  its  completion.  It  consisted 
in  the  exposure  of  "buckles"  or  short  strips  of  sheet 
lead  to  the  fumes  of  strong  vinegar  or  acetic  acid,  and 
the  introduction  of  carbon  dioxide.  This  gas  was  ob- 
tained from  tan  bark  which  was  used  to  cover  the  pots 
containing  the  lead  and  acid.  The  heat  needed  was 
obtained  by  the  decomposition  of  refuse  from  stables 
with  which  the  pile  of  pots  was  covered.  At  the  pres- 
ent time  most  of  the  commercial  supply  is  manufac- 
tured by  a  more  rapid  process.  By  means  of  compressed 
air  with  an  apparatus  on  the  order  of  an  atomizer,  the 
molten  lead  is  made  into  a  fine  dust.  This  is  treated 
with  acetic  acid,  and  owing  to  the  finely  divided  condi- 
tion of  the  lead,  the  process  is  completed  in  a  few  days. 
Carbon  dioxide  is  then  introduced  or  sodium  carbonate 
added,  which  produces  the  basic  carbonate.  It  is  dried 
and  ground  in  linseed  oil.  White  lead  as  a  paint  has  one 
disadvantage  in  sections  where  much  soft  coal  is  used. 
Considerable  quantities  of  hydrogen  sulphide  are  pro- 
duced. This  gas  reacts  with  the  lead  compounds  form- 
ing the  sulphide,  PbS,  which  is  black.  The  paint  as  a 
result  becomes  grayish  in  color.  The  following  equation 
will  illustrate  the  interchange, 


Zinc  white,  the  other  common  white  paint,  when  thus 
treated  does  not  change  in  color,   for  the  reason  that 


408 


APPLIED    CHEMISTRY 


zinc  sulphide  is  a  pure  white  compound,  ZnO  +  H2S  — > 
H20  +  ZnS. 

14.  Lead  Chromate,  PbCr04. — Commercially  known  as 
chrome  yellow,  lead  chromate  is  probably  the  best  yellow 
pigment  to  be  had.     It  is  prepared  by  treating  lead  ace- 
tate in  solution  with  potassium  chromate  or  dichromate. 
Lead  chromate  is  insoluble  in  water,  hence  forms  a  pre- 
cipitate.   It  is  filtered  out,  washed,  and  dried.     For  use 
it  is  ground  in  oil. 

15.  Other  Compounds. — The  chloride,  PbCl2,  nitrate, 
Pb(N03)2,  and  sulphate,  PbS04,  are  three   well-known 
compounds,  but  they  have  few  practical  uses  and  need 


Fig.  69. — A  battery  "grid." 

not  be  considered  here.  Lead  iodide,  dissolved  in  boil- 
ing water  and  allowed  to  cool,  crystallizes  out  again 
in  beautiful  golden  scales. 

16.  Storage  Batteries.— In  this  day  of  motor  cars  a 
study  of  lead  would  hardly  be  complete  without  some- 
thing about  storage  batteries.  Each  cell  of  a  storage 
battery  consists  of  a  number  of  lead  plates  or  "grids" 
separated  from  each  other  by  thin  sheets  of  wood.  One 
set  of  these  grids  is  connected  to  the  positive  post  or 
pole  and  the  other  alternating  set  to  the  negative  post. 
The  wood  serves  to  keep  them  from  touching  each  other 
yet  does  not  prevent  the  passage  of  the  ions  from  one 
plate  to  another.  These  grids  are  not  solid  sheets  of 


THE    LEAD    FAMILY  409 

lead  but  mere  skeletons  like  the  registers  over  hot-air 
furnace  pipes  as  shown  in  Fig.  69.  One  set  is  packed 
tightly  with  lead  dioxide  or  with  red  lead  or  both  mixed: 
the  other  set  with  finely  divided  lead.  They  are  then 
placed  in  a  container  with  dilute  sulphuric  acid  as  the 
electrolyte.  In  charging  the  battery  a  current  is  led 
in  from  a  dynamo  during  which  time  the  lead  dioxide 
is  the  anode.  To  this  the  sulphate  ions  will  be  attracted, 
which  in  combining  with  the  lead  oxide  will  give  up  their 
negative  charge  and  convert  a  portion  of  the  oxide  into 
sulphate.  The  hydrogen  ions  of  the  sulphuric  acid  will 
move  to  the  cathode,  and,  giving  up  their  charge,  the 
hydrogen  escapes,  leaving  the  lead  plate  positively 
charged.  Two  to  three  days  are  needed  in  bringing  the 
battery  up  to  the  desired  strength.  When  put  into  serv- 
ice, what  was  the  negative  pole  or  cathode  now  be- 
comes the  positive  pole.  The  reverse  process  now  takes 
place;  the  lead  is  slowly  converted  into  sulphate  as 
it  loses  its  positive  charge  and  the  sulphated  oxide  at  the 
other  pole  is  slowly  reduced  to  oxide  again  by  the  hy- 
drogen ions  which  move  in  that  direction. 

Exercises  for  Review 

1.  Name  the  metals  of  the  lead  group.     Look  up  the  table  and 
see  if  any  other  elements  belong  in  the  same  family. 

2.  What   can  you   say   of  the   occurrence   of   tin?     What   is  the 
name  of  the  only  ore? 

3.  Describe  tin.     Under  what  conditions  may  the  amorphous  va- 
riety form  ? 

4.  What  is  tin  plate?     Give  some  of  the  uses  for  tin  plate. 

5.  Give  some  other  uses  for  tin.    Name  its  more  important  alloys. 

6.  What  two  classes  of  compounds  does  tin  form?     Why  is  stan- 
nous  chloride  a  reducing  agent? 

7.  Name  the  oxides  of  tin  and  give  formulas. 

8.  What  is  the  chief  ore  of  lead?     Where  found  in  the  United 
States? 


410  APPLIED    CHEMISTRY 

9.  Describe  lead.    Where  is  it  in  the  electromotive  series?    What 
does  this  tell  one  about  the  reaction  of  a  metal  with  an  acid? 

10.  Give  the  more  important  uses  of  lead. 

11.  How  is  lead  pipe  used?     How  made? 

12.  Name  three  oxides  of  lead  and  give  formulas. 

13.  How  is  sugar  of  lead  made?     Write  equation. 

14.  What  is  white  lead?     How  formerly  made?     How  made  at 
present? 

15.  What  is  chrome  yellow?     What  is  its  use? 

16.  Describe  the  construction  of  a  storage  battery. 

17.  What  is  an  electrolyte?     What  is  the  electrolyte  in  a  stor- 
age battery? 

18.  Why  do  instructions  in  regard  to  care  of  storage  batteries 
tell  one  not  to  bring  a  lighted  match  near? 

19.  If  the  water  in  the  battery  did  not  evaporate  at  all,  would 
it  still  be  necessary  to  add  distilled  water  occasionally?     Explain 
your  answer. 

20.  Complete  the  following  equations  using  amounts  as  may  be 
needed, 

PbCl2  +  H,S04  -»  , 
Pb(NO,)2  +  KI  — »  , 
Pb  +  H2SQ4  ->  , 
PbCL,  +  K.CrO,  ->  , 
PbO  +  HN03  ->  , 
Pb  +  HNO3  -»  , 
PbS  +  02  -»  . 


CHAPTER  XXXIV 

THE  CHROMIUM  FAMILY 

Outline — 

Members  of  the  Group 
Chromium 

(a)    Preparation 

(&)   Characteristics 

(c)  Uses 

(d)  Compounds 

(a)  Chromates 

(b)  Bichromates 

(c)  Chromic  Salts 
Tungsten 

Uranium 

1.  Members   of  the   Group. — To    this    group    belong 
chromium,  molybdenum,  tungsten  and  uranium,  all  of 
them  rather  unfamiliar  elements.     Their  higher  oxides 
all  show  a  valence  of  six  as  would  be  expected  from 
their  position  in  the  table.     Chromium  has  an  atomic 
weight  of  52,  molybdenum,  of  96 ;  tungsten,  184 ;  ura- 
nium, 238.5. 

2.  Preparation  of  Chromium. — The  easiest  method  of 
obtaining  chromium  is  by  the  thermit  process  in  which 
chromic  oxide  is  substituted  for  the  ferric  oxide.     This 
has  been  described  on  p.  397. 

3.  Characteristics  of  Chromium. — Chromium  is  a  metal 
of  very  high  melting  point,  steel-gray  in  color  and  very 
hard.      It    does   not   tarnish   readily   in   the    air.     With 
warm  hydrochloric  acid  it  reacts  with  the  evolution  of 
hydrogen. 

4.  Uses. — The  chief  use  of  chromium  is  in  making  an 
alloy  with  steel  which  is  called  chrome  steel.     It  pos- 

411 


412  APPLIED    CHEMISTRY 

sesses  unusual  hardness  and  resistance  to  stress.  It  is 
used  in  parts  of  machinery  as  motor  cars  and  trucks 
where  great  strength  is  required. 

5.  Classes  of  Compounds. — Chromium  forms  several 
series  of  compounds   of  interest   to   the  chemist.     The 
oxide,  Cr03,  is  acidic,  the  anhydride  of  chromic  acid, 
corresponding  to   sulphuric  acid.     With  the   metals  it 
forms  a  number  of  salts  called  chromates.     One  of  the 
most  common  of  these  is  potassium  chromate,  K2O04, 
a  crystalline  salt  of  lemon-yellow  color.    Prom  the  chro- 
mates by  treatment  with  an  acid,  another  set  of  salts 
is  obtained,  called  the  dichromates,  of  which  potassium 
dichromate,  K2Cr207,  is  the  most  common.     Its  formula 
might  be  written,  K2O04.O03.    Another  oxide  of  chro- 
mium gives  a  series  of  salts  in  which  chromium  is  the 
positive  ion.    Thus  chromic  oxide,  Cr203,  is  a  basic  oxide 
with  the  corresponding  hydroxide,  Cr2(HO)G,  also  writ- 
ten Cr(HO)3.     Theoretically  it  is  formed  thus, 

Cr203  +  3H20  ->2Cr(HO)8. 

If  to  this  acids  are  added  we  obtain  the  corresponding 
salts.  Chromic  compounds  are  mostly  green  or  violet; 
in  fact,  the  word  chromium  is  from  the  Greek  for  color, 
given  because  so  many  of  the  compounds  of  this  metal 
are  highly  colored.  The  following  equation  shows,  the 
preparation  of  the  sulphate, 

2Cr(HO)3  +  3H2S04  -»  Cr2(S04)3  +  6H20. 

6.  Conversion  of  One  Class  to  Another. — Very  readily 
these  compounds  may  be  changed  from  one  class  into 
another.     Since  the  dichromates  contain  an  anhydride, 
seen   when   potassium   dichromate   is    written,    K2Cr04. 
Cr03,  they  may  be  regarded  as  acid  salts.     The  addition 
of  an  alkali,  therefore,  should  neutralize  the  anhydride 
and  make  a  normal  salt  of  it.    In  other  words,  it  should 


THE    CHROMIUM    FAMILY  413 

become  a  eliminate.  This  actually  happens  as  shown 
by  the  following  equation, 

K2Cr04.CrO,  f  2K1IO  ->  2K,CrO4  +  II,<>. 

At  the  same  time  the  color  should  change,  as  it  does, 
from  orange  to  lemon-yellow.  On  the  other  hand,  the 
addition  of  an  acid  to  the  chromate  converts  it  into 
the  dichromate,  thus, 

2K2Cr04  +  H2S04   -»  K,S04  +  H20  +  K2(Y04.Cr03. 

Chromates  or  dichromates  treated  with  hydrochloric  acid 
and,  especially  if  a  reducing  agent  be  present,  are 
changed  into  green  salts  with  chromium  as  the  positive 
ion,  thus, 

K2Cr207  +  14HC1  ->  2CrCl3  +  7H20  +  2KC1  +  3C12 
2K2Cr04  +  3ILS  +  10HC1  ->  2CrCl3  +  8H20  -f  4KC1  +  3S. 

On  the  other  hand,  compounds  containing  chromium  as 
a  positive  ion  may  be  changed  to  chromates  by  heating 
with  an  alkali.  Oxygen  is  taken  up  from  the  air,  thus, 

4Cr(HO),  +  8XaIIO  +  302  -»  4Na2Cr04  +  10H20. 

7.  Chromic   Compounds. — Most  of  the   chromic   com- 
pounds   are    green    in    color;    however,    chromic    alum, 
K2Cr2(S04)4,  is  violet.     Chromic  oxide,  Cr20;i,  is  a  green 
powder.     It  is  used  as  a   pigment,   in   coloring   glass  a 
deep  green  and  in  artificial  emeralds.    Chromic  chloride, 
CrCl,.6H2O,  may  be  prepared  by  treating  chromium  hy- 
droxide with  hydrochloric  acid.     It  is  of  a  bright  green 
color.      Chromium    sulphate,    Cr2(SO4),.l OILO,    is    of    a 
reddish-violet   color,    made    by   treating   the   hydroxide 
with  sulphuric  acid. 

8.  Insoluble  Chromates. — Potassium  chromate  already 
named  is  readily  soluble  in  water.     If  to  this  is  added  a 


414  APPLIED    CHEMISTRY 

solution  of  lead  acetate  an  insoluble  compound  of  lead 
chromate  precipitates  out,  thus, 

K2Cr04  +  Pb(C2H302)2   ->  PbO04  +  2KC2H302. 

It  has  been  mentioned  already  as  a  bright  yellow  pig- 
ment. Chrome  red  is  a  basic  lead  chromate  with  the 
composition,  PbO.PbO04;  it  is  of  bright  red  color.  Sil- 
ver chromate,  Ag2Cr04,  of  deep  red  color  and  barium 
chromate,  BaCr04,  a  pale  yellow,  are  both  insoluble 
compounds. 

9.  Tungsten. — The  symbol  for  this  element  is  W.    De- 
posits of  tungsten  are  said  to  exist  in  both  South  Da- 
kota and  Colorado,  but  most  of  our  supply  is  imported. 
It  is   of  interest  mainly  because   of  the   fact  that  the 
filament  of  most  electric  light  bulbs  is  now  made  from 
it.     Such  lamps  give  a  much  whiter  and  more  brilliant 
light  than  the  old  carbon  ones.     For  the  same  candle 
power  tungsten  lamps  consume  much  less  current  and 
hence  are  much  less  expensive.     When  first  introduced 
they  were  very  fragile  and  required  most  careful  han- 
dling, hence  were  not  received  favorably  by  the  public. 
That   objection  has  now  been  removed   and   their   life 
is  practically  the  same  as  that  of  the  carbon  lamp,  that 
is  about  1,000  light  hours. 

10.  Uranium. — Uranium  has  the  highest  atomic  weight 
of  all  the  elements,  238.5.    It  is  also  remarkable  in  that, 
contrary  to  our  general  ideas  of  elementary  matter,  it 
has  the  property  of  disintegrating  and  forming   other 
elements.     Thus,  one  of  the  products  of  uranium  is  ra- 
dium, and  from  radium  by  a  similar  decomposition,  he- 
lium is  obtained.     So,  uranium  forces  us  to  the  conclu- 
sion that  at  least  some  elements  are  capable  of  self  dis- 
integration. 


THE  CHROMIUM  FAMILY  415 

Exercises  for  Review 

1.  Name  the  elements  of  the  chromium  group,  and  give  symbols. 
2.  What  is  the  simplest  method  of  obtaining  pure  chromium? 
«>.  Give  chief  properties  of  chromium. 

4.  For  what  is  chromium  used? 

5.  Name  three  classes  of  chromium  compounds  and  give  one  ex- 
ample of  each. 

G.  Name  two  oxides  of  chromium  with  formulas.  Which  one  is 
acidic?  Of  what  acid  is  it  the  anhydride? 

7.  Why  will  an  alkali  change  a  dichromate  into  a  chromate? 
Illustrate. 

S.  Show  how  chromates  may  be  changed  into  dichromates. 

9.  How  may  chromates  or  dichromates  be  changed  into  chromic- 
salts? 

10.  Name  three  chromic  salts  and  give  formulas. 

11.  Name    four    insoluble    chromates    and    give    formulas;    also 
uses,  if  any. 

12.  What  use  has  tungsten?     Why  are  such  lamps  desirable? 

13.  What  is  the  most  remarkable  property  of  uranium? 

14.  Complete  the  following  equations,  using  amounts  needed  to 
balance, 

Cr(HO)3  +  HC1  — »  , 
Cr(HO)3  +  H.SO,  ->  , 
Cr203  +  H2S04~  -*  , 
CrO3  +  H,O  ->  , 
Cr,O.,  +  H2O  ->  , 
K,CrO4  +  AgNO3  — »  , 
K,CrO4  +  BaCl2  ->  , 
PbCl2  +  K2CrO4  ->  . 

15.  In  Section  6,  remembering  that   reduction  consists  in  lower- 
ing the  valence  of  an  element  and  oxidation  is  the  reverse,  raising 
Ihe   valence,   has   chromium    been    oxidized    or    reduced   in   the    last 
three  equations  given? 

16.  In   the  first  two   equations  in   Section  6,  has  chromium   been 
oxidized  or  reduced?     Give  reason  for  vour  answer. 


CHAPTER  XXXV 

MANGANESE  AND  COMPOUNDS 
Outline — 

Manganese 

Relation  to  Other  Elements  in  the  Table 

Characteristics 

Compounds 

(a)    The  Oxides 

(&)   Manganic  Compounds 

(c)  Manganates 

(d)  Permanganates 

1.  Position  in  Periodic  Table. — Manganese  is  found 
in  the  same  column  in  the  table  as  the  halogen  group, 
but  at  the  left  hand  side  of  the  space.    The  correspond- 
ing positions  in  the  long  periods  that  follow  manganese, 
by  looking  at  the  table  are  seen  to  be  vacant.     So  at 
present  this  element  is  all  alone. 

2.  Characteristics. — In   some   respects   manganese  re- 
sembles iron.     It  occurs  in  nature  as  a  dioxide,  Mn02, 
called  pyrolusite,  always  mixed  with  iron.     It  is  a  gray- 
ish metal,  with  the  power  of  reacting  with  dilute  acids 
and  evolving  hydrogen.    It  forms  an  alloy  with  iron  and 
is  tarnished  when  exposed  to  the  air.     Its  chief  use  is  in 
making  manganese  steel,  by  alloying  it  with  iron. 

3.  The  Oxides. — Manganese  forms  five  oxides  most  of 
which  are  of  no  great  importance.     The  lowest  is  MnO, 
which  is  a  basic  oxide;  as  they  increase  in  amount  of 
oxygen,  as  might  be  expected,  they  become  more  acidic 
until  the  highest  is  reached,  Mn207,  which  is  strongly 
acidic.     The  dioxide  is  the  most  familiar  to  the  student 
because  he  has  used  it  on  several  occasions.     The  hepr 

416 


MANGANESE    AND    COMPOUNDS  417 

toxide  shows  the  metal  to  have  the  combining  power 
or  valence  of  seven  as  would  be  expected  from  its  posi- 
tion in  the  table.  We  have  used  the  dioxide  catalyti- 
cally  in  making  oxygen,  and  as  an  oxidizing  agent  in 
the  preparation  of  bromine  and  chlorine.  It  is  a  basic 
oxide  and  unites  readily  with  acids  to  form  manganous 
salts. 

4.  Manganous  Salts. — Manganese  forms  both  mangan- 
ous and  manganic  salts  just  as  chromium  does,  but  the 
manganous  are  the  more   common.     They  may  be   ob- 
tained from  manganese  dioxide  by  treatment  with  an 
acid.     Thus  manganese  dioxide  with  hydrochloric  acid 
gives  the  chloride, 

Mn02  +  4HC1  ->  MnCl2  +  2H20  +  C12. 

On  evaporation  the  solution  gives  a  pink  crystalline  hy- 
drate, with  the  formula,  MnCl2.4H20.  The  sulphate  may 
be  obtained  by  treating  the  dioxide  with  sulphuric  acid, 
thus, 

2Mn02  +  2H2S04  ->  2MnS04  +  2H20  +  02. 

It  is  also  a  pink  hydrate,  but  the  quantity  of  water 
varies  at  different  temperatures.  At  ordinary  condi- 
tions the  formula  is  MnS04.5H20.  Manganous  salts 
or  the  dioxide,  fused  with  borax,  impart  an  amethyst 
color  to  the  bead. 

5.  Manganates  and  Permanganates.— Manganese  forms 
a    series    of    salts    known    as    manganates,    of    which 
potassium  manganate,  K2Mn04,  is  one  of  the  more  com- 
mon.    The  permanganate,  KMn04,  is  a  much  more  im- 
portant compound.     It  is  a  purple  solid  with  greenish 
luster,   and   crystallizes   in   small   rhombic   prisms.     In 
solution  it  gives  a  deep  purple  color.     It  has  frequent 
use  in  the  chemical  laboratory  in  estimating  the  quantity 


418  APPLIED   CHEMISTRY 

of  iron  and  in  various  other  ways.    It  is  sometimes  used 
in  cisterns  for  oxidizing  the  organic  impurities  present. 

Exercises  for  Review 

1.  Give  the  location  of  manganese  in  ths  table. 

2.  How   does  the  element  occur  in  nature! 

3.  Give  the  chief  properties  of  manganese. 

4.  What  is  the  chief  use  of  manganese? 

5.  How  many  oxides  of  manganese  are  there?     Name  two  and 
state  whether  basic  or  acidic. 

6.  Describe  the  appearance   of  manganese   dioxide.     What  uses 
has  it? 

7.  How  may  manganous  chloride  be  made?     Describe  it. 

8.  Describe  potassium  permanganate.     Give  its  uses. 

9.  Complete  these   equations,   using  such  amounts  as  are  neces- 
sary, 

MnO2  +  HBr  — »  , 
MnO,  +  HC1  ->  , 
Mn2O7  +  H2O  -^  , 
Mn(HO)2  +  H,SO4  -»  , 
MnCl2  +  KHO  ->  , 
MnSO4  +  Ca(HO),  -»  . 

10.  In  the  following   equations,   what-  substances  have  been   re- 
duced and  what  oxidized? 

MnO2  +  4HC1  ->  MnCl2  +  2H2O  +  CL,, 

2KMnO4  +  8ILSO.   I-  10FeSO4  ->  5Fcs(O4)3  +  K2SO4  +  2MnSO4  4 


CHAPTER  XXXVI 

THE  IRON  GROUP 

Outline — 

Members  of  the  Group 
Iron 

(«)   Occurrence 

(6)   Reduction  of 

(c)  The  Blast  Furnace 

(d)  Wrought  Iron 

(e)  Steel 

(«)   Cementation  Process 
(&)   Bessemer  Process 

(c)  Open  Hearth  Process 

(d)  Characteristics 

(e)  Method  of  Tempering 
(/)   Varieties  of 

General  Characteristics  of  Iron 
Compounds 

(«)   Ferrous  Sulphate 
(ft)   Ferric  Chloride 
Oxidation  and  Reduction  of  Salts 
Pigments 
Nickel 

(rt)   Characteristics 
(5)   Uses 
(c)   Compounds 
Cobalt 

(fl)   Characteristics 
(ft)   Compounds 

1.  Members  of  the  Group.— Iron,  nickel  and  cobalt  are 
usually  associated,  but  not  as  a  periodic  group.  They 
have  atomic  weights  close  together  and  do  not  form  a 
vertical  column  in  the  table.  Two  of  them  are  elements 
of  importance,  iron  being  intrinsically  the  most  valuable 
of  all  metals. 

419 


420  APPLIED    CHEMISTRY 

2.  Occurrence  of  Iron. — There  are  several  ores  of 
iron  used  in  the  preparation  of  the  metal.  Of  these, 
hematite,  Fe203,  is  the  most  important.  It  is  a  dark 
colored  mineral,  reddish-brown  to  black,  which  drawn 
across  a  piece  of  unglazed  porcelain  gives  a  dull  red 
streak.  It  is  this  fact  that  gave  the  name  to  the  ore, 
the  word  hematite  being  from  the  Greek  meaning  blood. 
Limonite,  which  is  a  hydrated  oxide,  Fe203.3H2O,  gives 
a  yellow  streak,  and  received  its  name  from  the  Latin 
word  for  lemon.  In  some  sections,  the  magnetic  oxide, 
Fe304,  is  found.  The  carbonate,  FeC03,  called  siderite, 
and  the  disulphide,  FeS2,  commonly  known  as  "fool's 
gold"  should  also  be  mentioned.  Iron  never  occurs  free 
upon  the  earth  except  in  very  minute  quantities.  Meteo- 
rites have  been  discovered  containing  from  92  to  97  per 
cent  of  iron  and  the  remainder  nickel.  Lieutenant  Peary, 
some  years  ago,  in  one  of  his  Arctic  trips  discovered 
through  the  aid  of  his  Esquimos  two  large  meteorites, 
one  of  which  weighed  in  the  neighborhood  of  100  tons, 
the  largest  ever  found.  Later,  he  brought  this  one  back 
to  the  Brooklyn  Navy  Yards.  In  the  form  of  compounds, 
iron  is  found  everywhere.  It  is. the  most  common  coloring 
agent  in  rocks  and  soils,  and  exists  in  many  food  prod- 
ucts and  in  the  blood. 

3.  Reduction  of  Iron. — It  will   be   remembered   that 
zinc  is.  reduced  from  its  chief  ore  by  means  of  coke, 
after  the  preliminary  roasting  has  converted  the  sulphide 
into  an  oxide.     Since  most  of  the  iron  ores  are  already 
oxides,    this  -  preliminary    treatment    is    not    necessary. 
Coke  is  used  to  furnish  the  heat  and  the  carbon  for  the 
reduction. 

4.  The  Blast  Furnace. — The   ordinary   blast   furnace 
varies  from  20  to  25  feet  in  diameter  and  from  75  to 
90  feet  in  height,    It  is  made  of  fire  brick  and  strength- 


THE    IRON    GROUP 


421 


ened  011  the  outside  by  heavy  boiler  plate  iron.  The  top 
of  the  furnace  is  so  constructed  that  it  is  practically  air- 
tight, and  any  gases  formed  within  must  pass  off 
through  a  pipe  near  the  top  shown  in  Fig.  70.  How- 
ever, as  the  process  is  a  continuous  one,  additions  of 


Fig.  70. — A  blast  furnace  for  preparing  cast  iron. 


422  APPLIED    CHEMISTRY 

material  are  made  repeatedly  through  a  hopper  which 
opens  mechanically  when  a  load  is  dumped  upon  it  and 
then  closes  again  when  the  material  has  fallen  into  the 
furnace.  Near  the  bottom  is  an  opening  for  drawing 
off  the  molten  iron,  which  is  kept  closed  by  means  of 
clay  until  needed.  At  some  distance  above  is  an  open- 
ing for  the  exit  of  the  slag.  As  the  quantity  is  usually 
large,  this  is  open  most  of  the  time  with  a  steady  outflow 
of  the  molten  material.  Above  this,  entering  from  the 
sides,  are  the  blast  pipes,  often  called  tuyeres,  through 
which  the  air  is  forced  into  the  furnace.  This  is  needed 
to  give  the  intense  heat  required.  The  furnace  is  tapped 
usually  every  twelve  hours  and  the  molten  iron  run  off 
into  trenches  and  side  trenches  in  the  ground.  These 
short  trenches  are  called  "pigs"  and  the  iron  formed  in 
them  "pig  iron."  Sometimes  the  molten  iron  is  run  into 
steel  molds  bolted  upon  an  endless  chain,  which  moves 
slowly  forward  as  each  is  filled  from  a  large  cauldron. 
(See  Fig.  71  for  illustration  of  method  of  molding  pig 
iron.) 

5.  The  Charge. — The  materials  used  in  the  "charge" 
put  into  the  furnace  are  usually  iron  ore,  coke  and  lime- 
stone.    Most  ores  when  brought  from  the  mine  contain 
more  or  less  silica.     In  the  furnace  the  limestone  with 
the  silica  forms  a  species  of  glass,  called  slag.    It  floats 
above  the  molten  metal  and  protects  it  from  the  oxidizing 
action  of  the  blasts  of  air.    When  the  ore  contains  lime- 
stone as  a  gangue,  instead  of  silica,  some  silicious  material 
is  added  to  serve  as  the  flux. 

6.  The  Chemical  Action. — Owing  to  the  large  amount 
of  air  introduced  through  the  tuyeres,  at  the  bottom  of 
the  furnace  carbon  dioxide  is  produced.     (See  p.  169.) 
As  this  flows  upward  it  meets  red-hot  carbon  and  is 
changed  to  carbon  monoxide,  thus, 


THE    IRON    GROUP 

CO.,  +  C  -»  2CO. 


423 


This  being  an  unsaturated  gas  removes  the  oxygen  from 
the  iron  ore  and  the  free  iron  thus  produced  flows  to 
the  bottom  of  the  furnace.  The  gas,  which  escapes  at 
the  top,  contains  much  carbon  monoxide  as  well  as  other 
combustible  gases.  This  is  used  to  heat  the  air  forced 


71. — A    blast    furnace,    showing    the    molds    for    the    "pigs"    in    the    sand, 


424  APPLIED    CHEMISTRY 

in  and  to  run  the  fans  for  the  air  pressure.  The  iron 
thus  obtained  is  known  as  cast  iron.  It  contains  a  high 
percentage  of  carbon,  sometimes  as  much  as  3  or  4  per 
cent  as  well  as  silica  and  other  impurities.  It  is  coarse 
grained,  brittle,  hard,  and  has  a  melting  point  relatively 
low,  about  1250°  C. 

7.  Wrought  Iron. — Wrought  iron  is  made  by  heating 
the   cast   iron   in   a   reverberatory   furnace   with   ferric 
oxide.     The  purpose  of  the  oxide  is  to  furnish  oxygen 
for  union  with  the  carbon  in  the  iron,  by  which  carbon 
monoxide  is  formed.     These  are  sometimes  called  pud- 
dling furnaces,  because  the  molten  pig  iron  is  " puddled" 
or  stirred  so  as  to  facilitate  the  action.    When  the  mass 
has  become  stiff  and  very  difficult  to  stir,  it  is  known  that 
the  carbon  is  burned  out.     Pure  iron  melts  with  much 
more  difficulty  than  impure,  and  the  temperature  of  these 
furnaces  is  only  sufficient  to  keep  the  impure  form  in  a 
molten  condition.     It  is  the  same  principle,  seen  often 
before,  in  which  a  solution  will  remain  liquid  while  the 
solvent   will   solidify.     At   this   stage   the   iron,    called 
"bloom,"  is  removed  from  the  furnace,  and  beaten  with 
trip  hammers,  which  forces  out  the  silica  and  any  slag 
remaining.     Such  is  now  wrought  iron.     It  is  malleable 
and  may  be  welded;  it  is  fine  grained,  somewhat  more 
dense  than  cast  iron,  melts  at  about  1,500°  C.  and  contains 
only  about  0.1  to  0.2  per  cent  of  carbon.     It  should  not 
contain  much  phosphorus  or  sulphur.     Wrought  iron  is 
made  into  sheets,  and  is  used  in  chains,  wire,   and  in 
many  other  ways  where  a  cheap,  malleable  metal  is  de- 
sired. 

8.  Steel. — The  oldest  method  of  making  steel  was  by 
the  cementation  process.    Bars  of  wrought  iron  were  im- 
bedded in  powdered  charcoal  and  heated  strongly  for  a 
number  of  days.    The  iron  slowly  absorbed  small  portions 


THE    IRON    GROUP  425 

of  the  carbon  and  was  changed  thereby  into  steel.  How- 
ever, it  was  far  from  satisfactory,  for  the  reason  that  the 
carbon  was  not  taken  up  uniformly.  Some  portions  would 
contain  so  much  as  to  be  more  or  less  brittle,  while  others 
would  not  contain  enough.  Cast  steel  was  first  made  by 
melting  cementation  steel  and  molding  it  into  a  bar  so  as 
to  give  uniform  composition.  This  greatly  improved  the 
produce  previously  obtained.  The  process  is  entirely  too 
slow  for  modern  demands;  for  years,  until  recently,  most 
of  the  steel  used  has  been  made  by  the  Bessemer  process 


Fig.  72. — The  Bessemer  converter. 

(Fig.  72).  This  process  uses  a  movable  furnace,  called 
a  converter,  made  of  boiler-plate  iron  and  lined  with  a 
silicious  earth  called  ganister,  which  is  infusible.  The 
compressed  air  passes  up  through  a  supporting  post, 
through  the  horizontal  trunnion,  and  down  the  pipe  into 
the  tuyere  box  or  air  chamber,  then  into  the  body  of  the 
converter.  For  use  it  is  filled  half  or  two-thirds  with 
molten  cast  iron  and  the  air  is  turned  on.  No  heat  is  ap- 
plied ;  the  interaction  of  the  oxygen  of  the  air  with  the  car- 
bon and  other  impurities  in  the  iron  is  sufficient  not  only 
to  keep  the  metal  molten,  but  even  raise  the  temperature. 


426  APPLIED    CHEMISTRY 

At  first  luminous  flames  and  great  showers  of  sparks  shoot 
from  the  mouth  of  the  converter,  but  as  the  carbon  is 
burned  out  the  action  becomes  more  quiet  until  finally 
it  practically  ceases  altogether.  If  the  product  obtained 
at  this  stage  were  hammered,  it  would  form  wrought  iron. 
For  steel  a  definite  amount  of  spiegel  iron  is  added.  This 
is  an  iron-manganese  alloy  which  may  have  as  high  as 
20  per  cent  of  manganese,  but  usually  only  a  small  pro- 
portion. It  contains  also  a  fixed  amount  of  carbon  so 
that  any  required  proportion  of  carbon  may  be  thus  put 
back  into  the  iron  to  form  the  steel.  The  blast  of  air 
is  continued  just  long  enough  to  mix  the  spiegel  thoroughly 
with  the  other  when  the  whole  is  poured  out  and  cast 
into  ingots.  It  will  be  seen  that  the  process  consists  in 
burning  out  all  the  carbon  and  then  restoring  whatever 
may  be  desired  for  a  particular  variety  of  steel.  This 
method  works  successfully  unless  phosphorus  be  present 
in  the  cast  iron.  The  Bessemer  converter  will  not  remove 
phosphorus,  and  its  presence  makes  steel  brittle.  To  re- 
move it,  a  converter  lined  with  lime  is  used.  Phosphorus, 
being  an  acidic  element,  unites  with  the  lime,  a  basic  oxide, 
forming  the  superphosphate  of  calcium,  mentioned  on  p. 
281  as  a  valuable  fertilizer.  This  modified  plan  is  called 
the  basic  lining  or  the  Thomas-Gilchrist  process. 

9.  Open  Hearth  Steel. — In  the  last  few  years  much 
steel  has  been  made  by  what  is  known  as  the  open  hearth 
or  Siemens-Martin  process.  The  cast  iron,  whose  carbon 
content  is  known  by  chemical  analysis,  is  mixed  with  a 
definite  amount  of  hematite,  ferric  oxide,  or  some  other 
iron  ore,  and  heated  in  an  open  furnace  with  a  gaseous 
fuel,  for  about  ten  hours.  The  materials  are  so  propor- 
tioned as  to  leave  a  definite  amount  of  carbon  in  the  steel. 
The  gas  used  for  fuel  is  heated  before  being  burned  and  the 


THE    IRON    GROUP  427 

charge  is  tested  from  time  to  time  to  know  when  the  proc- 
ess is  complete. 

10.  Characteristics  of  Steel. — Steel  is  between  wrought 
and  cast  iron  in  content  of  carbon.     The  amount  varies 
from  0.5  to  1.5  per  cent.    Its  most  remarkable  property 
is  its  ability  to  be  tempered,  that  is,  to  be  so  treated  as 
to  hold  a  cutting  edge.     It  also  has   wonderful   tensile 
strength.    Wires  of  lead,  copper  and  steel,  of  equal  diam- 
eter, show  that  steel  will  withstand  twice  what  copper  will 
and  forty  times  what  lead  will.     This  is  one  of  the  chief 
reasons  for  the  great  use  of  steel  in  the  arts. 

11.  Tempering  Steel. — If  a  piece  of  steel  is  heated  to 
redness  and  then  cooled  sloAvly  it  is  soft  and  malleable 
like  wrought  iron ;  but  if  so  heated  and  cooled  suddenly 
it  is  hard  and  brittle.     Now  if  it  be  heated  again  to  a 
much   lower   temperature,   ranging  from   225°    to   325° 
C.,  it  assumes  degrees  of  hardness  and  brittleness  be- 
tween these  two  conditions  and  is  suitable  for  cutting 
instruments.      At    the    lower    temperature,    such    keen- 
edged  instruments  as  razors  and  instruments  employed  in 
surgery  are  made;  at  the  higher,  saws  and  similar  tools. 
The  explanation  of  this,  put  as  simply  as  possible,  is  as  fol- 
lows.     At    the    temperature    first    used    a    considerable 
amount    of   iron    carbide    is   formed   which   makes   the 
steel  brittle.     If  the  bar  is  cooled  suddenly  the  carbide 
remains  in  the  steel;  if  cooled  slowly  the  carbide  de- 
composes and  leaves  less  of  it  in  the  steel.     At  the  sec- 
ond heating,  if  only  a  low  temperature  is  used,  not  so 
much  time  is  given  in  cooling  for  the  iron  carbide  to 
be  decomposed ;  hence,  a  considerable  amount  remains 
and  the  steel  is  harder  and  takes  a  keener  edge,  but  is 
more   brittle.     When   heated   to   a   higher   temperature 
more  time  is  given  for  the  carbide  to  be  decomposed ; 
hence,   the   steel  is  left  softer,   less  brittle  and  better 


428  APPLIED    CHEMISTRY 

suited  for  rough  tools,  but  not  capable  of  so  keen  an 
edge. 

12.  Kinds  of  Steel. — By  mixing  in  the  converter  one 
or  more  of  some  of  the  rarer  metals,   alloys  of  great 
value  may  be  obtained.    As  they  consist  mainly  of  steel 
they  are  spoken  of  as  such.     Chrome  steel  contains  a 
small  percentage  of  chromium  or  sometimes  both  chro- 
mium and  vanadium.     It  is  a  steel  of  special  strength 
and  is  used  in  parts  of  machinery  where  great  strain 
may  come,   as  in  the  axles  and  frames   of   motor  cars. 
Nickel  steel  may  contain  as  much  as  4  per  cent  of  nickel 
and  is  especially  desirable  as  armor  for  war  vessels.     It 
has  great  strength,  is  very  tenacious,  hard  to  pierce  with 
projectiles,  and  resistant  to  sea  water.    A  manganese  steel 
gives  a  variety  used  for  making  burglar  proof  safes  of 
very  great  hardness. 

13.  General   Characteristics   of  Iron. — The   most   im- 
portant physical  properties  have  been  given  in  describ- 
ing the  different  varieties  of  iron.     It  is  well  up  in  the 
electromotive  series  of  metals  and  readily  displaces  hy- 
drogen from  dilute  acids.    Very  concentrated  nitric  acid 
products  a  singular  condition  known  as  the  passive  state 
in  which  it  will  not  react  with  dilute  acids  with  the  evo- 
lution of  hydrogen.     Chromium  is  affected  in  a  similar 
manner.     Hammering  will  restore  its  former  properties; 
In  oxygen,  iron  when  heated  burns  readily  with  a  beauti- 
ful shower  of  sparks,   and  forms  mainly  the   magnetic 
oxide,   Fe3O4.     Superheated   steam,   directed   upon   iron, 
gives  it  a  blue  color  due  to  the  formation  of  a  closely-ad- 
hering, protecting  film  of  this  same  oxide.    In  the  air,  in 
the  presence  of  moisture,  ferric  oxide,  Fe203,  is  formed; 
this  being  nonadhering,  the  metal  becomes  entirely  cor- 
roded. 


THE   IRON    GROUP  429 

14.  Compounds  of  Iron. — Iron  forms  two  classes  of 
compounds,  ferrous  and  ferric.  The  former  are  mostly 
green  in  color,  the  latter  brown.  Ferrous  compounds 
are  unsaturated  and,  as  a  rule,  tend  to  become  oxidized 
to  the  ferric. 

Ferrous  sulphate,  FeS04.7H20,  is  commonly  known 
by  the  name  of  green  vitriol,  or  copperas.  It  is  an 
efflorescent  hydrate,  but  as  it  loses  its  water,  it  also  be- 
comes oxidized  from  the  air  and  forms  a  basic  ferric 
sulphate.  Therefore,  unlike  effloresced  blue  vitriol,  the 
addition  of  water  does  not  re-form  the  ferrous  sulphate. 
It  is  used  in  various  wa}Ts.  Common  black  ink  is  a  mix- 
ture of  ferrous  sulphate  and  tannic  acid,  which  on  ex- 
posure changes  into  a  black  ferric  salt.  To  give  it  more 
body  some  mucilage  is  usually  added  and  often  some  dye 
as  well.  Ferrous  chloride,  FeCl2,  may  be  made  by  dis- 
solving iron  in  dilute  Iwdrochloric  acid.  It  is  a  very  un- 
stable salt  and  rapidly  oxidizes  to  a  ferric.  Ferrous 
hydroxide,  Fe(HO)2  may  be  prepared  by  adding,  to 
any  soluble  ferrous  salt,  a  solution  of  some  alkali.  If 
pure  it  is  white  in  color,  but  as  usually  obtained  is 
greenish,  changing  rapidly  to  brown  as  it  is  oxidized 
by  the  air.  The  double  salt,  ferrous  ammonium  sulphate, 
(NH4)2S04.FeS04.6H20,  is  the  most  stable  of  the  ferrous 
salts.  It  is  pale  green  in  color,  crystalline  in  structure 
and  soluble  in  water.  For  experimental  work  in  the  lab- 
oratory it  is  far  the  best  for  use. 

15.  Ferric  Compounds. — Ferric  chloride,  FeCl8.GH,O, 
is  a  very  deliquescent,  brown  solid.  It  is  employed  in 
most  pharmaceutic  preparations  of  iron.  Mention  has 
been  made  of  its  use  in  preparing  the  best  antidote  for 
arsenic.  Ferric  sulphate,  Fe2(SO4).{,  may  be  made  by  the 
oxidation  of  ferrous  sulphate  with  nitric  acid  or  bro- 
mine or  with  some  other  oxidizing  agent.  Ferric  hy- 


430  APPLIED    CHEMISTRY 

droxide,  Fe(HO)3,  may  be  prepared  by  treating  ferric 
chloride  with  ammonium  hydroxide  or  any  other  solu- 
ble hydroxide.  It  is  a  gelatinous,  brownish  colored 
precipitate.  Heated,  it  loses  water  and  becomes  ferric 
oxide,  Fe203. 

16.  Oxidation  and  Reduction  of  Iron  Compounds. — As 
stated  above,  ferrous  salts  may  be  readily  changed  to 
ferric  by  oxidation.     If  a  solution  of  ferrous  sulphate 
acidulated  with  sulphuric  acid  has  nitric  acid  added  and 
is  then  heated,  it  is  changed  into  ferric  sulphate,  thus, 

2FeS04  +  H2S04  +  2HN03  ->  Fe2(S04)3  +  2H20  +  2N02. 

Potassium  permanganate  is  used  to  oxidize  ferrous  salts 
to  ferric  in  the  same  way.  As  it  is  of  a  deep  violet,  a 
coloration  of  the  iron  solution  is  seen  as  soon  as  the  oxi- 
dation is  completed.  A  permanganate  solution,  there- 
fore, of  known  strength,  may  be  used  to  determine  the 
amount  of  iron  present,  by  noting  the  number  of  cubic 
centimeters  needed  to  oxidize  a  certain  amount  of  the 
ferrous  solution.  The  equation  is 

2KMn04  +  8H2SO  .+  10FeS04  -> 

5Fe2(S04)3  +  K2S04  +  2MnS04  +  8H20. 

Conversely,  ferric  salts  may  be  reduced  to  ferrous.  This 
is  easily  done  by  nascent  hydrogen,  thus, 

2FeCl3  +  2H  -*  2FeCl2  +  2HC1. 

The  hydrogen  may  be  obtained  by  putting  pieces  of  zinc 
into  the  ferric  solution  and  adding  a  dilute  acid  as 
hydrochloric.  In  a  similar  way  hydrogen  sulphide  re- 
duces iron  salts  in  the  presence  of  an  acid,  thus, 

2FeCl3  +  H2S  -*  2FeCl2  +  2HC1  +  S. 
The  sulphur  is  precipitated. 

17.  Other  Iron  Compounds. — There  are  a  few  com- 
pounds in  which  iron  forms  a  part  of  the  negative  ion. 
Such  are  potassium  ferrocyanide,  K4Fe(CN)6,  and  ferri- 


THE   IRON   GROUP  43.1 

cyanide,  K3Fe(CN)fl.  These  were  formerly  regarded  as 
double  salts  as  their  present  names  indicate.  Potassium 
ferrous  cyanide  was  regarded  as  Pe(CN)2.4KCN  and 
the  other  as  Fe(CN)s.3KCN.  If  really  double  salts,  as 
last  written,  the  former  would  in  solution  contain  fer- 
rous ions,  and  the  latter  ferric  ions.  Chemical  tests  show 
this  is  not  true.  Mixed  with  ferric  or  ferrous  salts,  they 
give  compounds,  one  of  which  is  known  as  Prussian  blue, 
Fe4[Fe(CN)6]3,  which  was  formerly  used  frequently  in- 
stead of  indigo  as  a  cheap  bluing  in  laundry  work.  Both 
of  the  cyanide  compounds  have  use  in  the  laboratory  in 
making  delicate  tests  for  the  presence  of  iron. 

18.  Some  Pigments. — Rouge  is  the  commercial  name 
for  a  form  of  ferric  oxide  used  in  polishing.     It  is  made 
from  ferrous  sulphate  which  is  obtained  in  cleaning  iron 
for  the  purpose  of  galvanizing.    Venetian  Red  and  other 
cheap   red   pigments,   used   for   painting  roofs   and   out- 
buildings, are  largely  ferric   oxide  mixed  with  more  or 
less  clay.     Yellow  oclire  is  a  hydrated  form  of  the  same 
compound    and    corresponds    to    limonite,    already   men- 
tioned.    It  is  used  sometimes  for  priming  woodwork  and 
as  a  cheap  paint.     Raw  and  burnt  sienna  and  raw  and 
burnt  umber  are  other  well-known  pigments  of  similar 
composition,  two  of  them  obtained,  as  the  names  indicate 
by  strongly  heating  the  oxide. 

19.  Nickel,  its  Characteristics.— Nickel  is  a  hard  white 
metal  which  tarnishes  very  slowly  in  the  air.     It  is  sus- 
ceptible of  a  high  polish.     It  is  little  attacked   either 
by  dilute  hydrochloric  or  sulphuric  acid.     It   is  exten- 
sively used  in  plating  iron.     The  method  is  the  same  as 
described  in  the  case  of  the  other  metals,  except  a  dif- 
ferent solution  of  nickel  is  used.     The  double  sulphate 
of     nickel     and     ammonium,      (NH4).>S04.NiS04.(>II,(), 
gives  a  plating  which  adheres  best.     It  is  a  greenish  col- 
ored salt,  soluble  in  water.     Nickel  is  also  used  in  coin- 


432  APPLIED    CHEMISTRY 

age,  alloyed  with  copper  in  the  familiar  five-cent  piece; 
in  the  powdered  form  it  is  used  somewhat  in  wireless 
telegraphy  and  in  the  familiar  alloy,  German  silver.  Its 
use  in  making  nickel  steel  has  been  mentioned  as  well 
as  its  catalytic  action  in  the  hydrogenation  of  oils. 

20.  Compounds  of  Nickel. — Nickel  forms  two  series 
of  compounds,  nickelous  and  nickelic.     The  former  are 
the  more   common.     They   are   mostly   green   in   color; 
however,  fused  in  the  borax  bead,  they  give  a  brown 
coloration,   which   is   distinctive.     The   most   important 
salt  is  the  double  sulphate  already  mentioned  as  of  use 
in  plating. 

21.  Characteristics  of  Cobalt. — Cobalt  is  a  hard,  white 
metal  resembling  nickel.     It  has  no  uses.     It  forms  two 
classes  of  compounds,  cobaltous  and  cobaltic.     The  for- 
mer  are   the   more   common    and   the   more   important. 
They  are  deep  pink  or  reddish  in  color.    Fused  in  a  borax 
bead,  even  in  minute   quantity,  they  give  a  beautiful 
blue  color,  which  serves  to  identify  the  metal. 

22.  Uses  of  Cobalt  Compounds. — Some  very  valuable 
pigments  are  made  from  cobalt  compounds.     Smalt,  a 
kind  of  glass,  made  by  fusing  some  cobalt  compound  as 
the  oxide,  with  sand  and  potassium  nitrate,  is  of  a  deep 
blue  color.     It  is  powdered  and  mixed  in  the  paste  used 
on   the   outside   of   iron   vessels   in   the   manufacture   of 
' '  granite  ware. ' '    When  these  are  heated  strongly  in  ovens 
the  coating  melts  and  gives  the  familiar  blue  ware  in 
common  use.    It  is  also  ground  in  oil  and  used  as  a  paint 
for  chinaware.     Several  cobalt  salts  become  blue  in  color 
when  they  lose  their  water  of  combination.     Based  upon 
this  fact  is  the  "cobalt  barometer"  occasionally  seen.     It 
consists  of  a  strip  of  unsized  paper  or  cloth  moistened 
with  cobaltous  solution.    If  the  air  is  very  dry  the  paper 
turns  blue;  if  damp,  red.     Sympathetic  inks,  containing 
some  cobalt  compound,  depend  upon  the  same  property. 


THE  IRON   GROUP  433 

When  used  upon  paper  the  pink  color  is  scarcely  visible; 
if  warmed,  the  water  of  combination  is  removed  and  the 
compound  turns  blue.  It  then  may  be  plainly  read.  In 
damp  air  it  will  again  become  invisible. 

Exercises  for  Review 

1.  Name  the  metals  usually  associated  with  iron.     Why  do  they 
not  form  a  periodic  group  ? 

2.  Mention  the  chief  ores  of  iron  and  give  composition. 

3.  How  could  you  recognize  a  piece  of  hematite?     Of  limonite? 

4.  Describe  the  construction  of  the  blast  furnace. 

5.  Of  what   does  the  charge  put  into   a  blast   furnace   consist? 
What  is  the  purpose  of  each? 

6.  Describe   the  chemical  action   which  takes  place  in  the  blast 
furnace. 

7.  How  is  wrought  iron  made?     WThat  are  some  of  its  uses? 

8.  Describe  the  cementation  process  of  making  steel.     Why  was 
cast  steel  used? 

9.  Describe  the  Bessemer  converter  and  state  the  principle  un- 
derlying its  use. 

10.  What  is  the  Thomas-Gilchrist  process  of  making  steel? 

11.  Describe  the  open  hearth  process. 

12.  How  is  steel  tempered?     Explain  the  principle   underlying. 

13.  Name    some    different    kinds    of    steel    and    state    for    what 
adapted. 

14.  Give  the  chemical  properties  of  iron.     What  is  meant  by  the 
passive  state? 

15.  What   is   green   vitriol?      How    made?      Uses?     Name    some 
other  ferrous  compound. 

16.  Name  one  ferric  salt  and  tell  how  to  prepare  ferric  hydrox- 
ide from  it.     What  use  has  the  hydroxide? 

17.  How    can    ferrous    sulphate    be    changed    to    ferric?      Ferric 
chloride  to  ferrous?     What  is  oxidation  in  the  broad  sense? 

18.  Name  some  common  iron  pigments  and  give  uses  for  them. 
Of  what  do  they  consist? 

19.  Give  the  chief  characteristics  of  nickel  and  uses. 

20.  How  is  nickel  plating  done? 

21.  Name  one  important  compound  of  cobalt  and  give  important 
use  for  it. 

22.  What   is  a   sympathetic   ink?     Explain  how  one  made   from 
cobalt  compounds  works. 


CHAPTER  XXXVII 

THE  PLATINUM  AND  PALLADIUM  GROUPS 
Outline — 

Members  of  the  Group 

Occurrence 

Platinum 

(a)   Characteristics 

(6)   Uses 
Osmium 
Iridium 
Palladium 

1.  Members  of  the  Group. — Osmium,  iridium  and  plat- 
inum are  associated  as  are  iron,  nickel  and  cobalt,  but 
do  not  constitute  a  periodic   group,  for  their  weights 
run  consecutively  and  not  as  octaves.     Osmium  has  an 
atomic  weight  of  191,  iridium,  193,  and  platinum,  194.8. 

2.  Occurrence. — These  metals  are  found  as  grains  or 
small  nuggets  in  alluvial  deposits,  much  as  is  gold,  but 
in  very  limited  quantities.     California  produces  about 
all  there  is  obtained  in  the  United  States.     Nearly  the 
entire  world's  supply  comes  from  the  Ural  Mountains  in 
eastern   Russia.      The   three   metals   are   nearly   always 
found  mixed  together,  with  platinum  the  more  abundant. 
They  are  separated  by  difficult  chemical  processes  which 
would  not  be  of  interest  to  the  student. 

3.  Characteristics  of  Platinum. — Platinum  is  the  most 
important  metal  of  the  group.    It  is  steel-white  in  color, 
very  hard>  not  attacked  by  acids,  but  is  soluble  in  aqua 
regia,  or  nascent  chlorine.     It  is  exceedingly  malleable 
and    ductile,    and    when    heated    may    be    welded    like 
wrought  iron.     At  red  heat  it  easily  forms  alloys  with 

434 


PLATINUM    AND    PALLADIUM    GROUPS  435 

metals  of  low  melting  point,  such  as  lead  and  antimony 
and  will  also  combine  with  carbon,  phosphorus  and  sil- 
ica. The  alloys  mentioned  have  low  melting  points; 
hence,  the  greatest  care  must  be  exercised  not  to  heat 
any  such  metals  in  platinum  ware.  If  it  is  done,  the 
alloy  is  readily  formed,  and  then  melts  out  leaving  a 
hole  in  the  platinum  vessel.  Silica  and  phosphorus  ren- 
der platinum  brittle,  so  may  likewise  cause  serious  in- 
jury. If  pure,  platinum  has  a  high  melting  point  of 
about  1,700°  C.  When  finely  divided  it  has  great  power 
of  occluding  or  absorbing  hydrogen.  It  frequently  pos- 
sesses the  power  of  catalysis.  This  has  already  been  seen 
in  several  instances.  It  may  likewise  be  shown  by  hold- 
ing a  spiral  of  platinum  wire  in  the  neck  of  a  flask  of 
strong  ammonium  hydroxide,  slightly  warmed.  If  the 
wire  is  heated  before  being  thrust  into  the  neck  of  the 
flask  at  some  point  where  the  ammonia  and  air  are 
mixed,  the  wire  will  become  red  hot  and  so  continue  as  long 
as  the  current  of  ammonia  is  escaping.  The  wire  may 
even  be  withdrawn  from  the  flask  and  reinserted  when 
it  will  again  heat  up  as  before. 

4.  Uses  of  Platinum. — On  account  of  its  high  melting 
point  and  resistance  to  attack  by  acids,  platinum  is  em- 
ployed extensively  in  the  laboratory  in  the  form  of  cru- 
cibles, wire  and  foil.  In  late  years,  unfortunately  for 
science,  it  has  been  used  very  largely  in  jewelry.  Cata- 
lytically,  it  is  used  in  making  sulphuric  acid  by  the 
contact  process  (p.  261)  as  well  as  in  other  manufactur- 
ing processes.  In  dentistry  platinum  wire  is  used  as 
" posts"  in  fastening  artificial  teeth  to  the  plate.  It  is 
also  used  in  electric  lamps  as  the  connection  between  the 
inside  filament  and  the  outside  copper  wire.  This  is 
for  the  reason  that  platinum  has  practically  the  same 
rate  of  expansion  when  heated  as  glass:  any  metal  used 


436  APPLIED    CHEMISTRY 

thus  which  expands  more  than  glass  when  heated  by 
the  current  would  crack  the  lamp. 

5.  The  Other  Metals  of  the  Group. — Osmium  is  re- 
markable for  its  high  melting  point,  being  over  2,000° 
C.  Iridium  is  harder  than  platinum  and  is  sometimes 
alloyed  with  the  latter  for  the  purpose  of  securing  a 
metal  with  extreme  resistance  to  acids.  It  is  also  some- 
times used  on  the  tips  of  fountain  pens.  Palladium  is 
of  special  interest  because  of  its  remarkable  power  of 
absorbing  hydrogen  and  other  gases.  When  heated  it 
will  occlude  about  seven  hundred  times  its  own  volume 
of  hydrogen.  It  does  not  belong  with  the  platinum  met- 
als, but  is  the  most  important  metal  of  another  special 
group,  much  lighter  in  weight. 

Exercises  for  Review 

1.  Name    the    metals    of    the    platinum    group   and    give    atomic 
weights. 

2.  Why  can  these  three  not  be  regarded  as  forming  a  periodic 
group? 

3.  What   can   you   say   of  the   occurrence   of   the   metals   of  this 
group  ? 

4.  Give  the  important  characteristics  of  platinum. 

5.  What  precaution  must  be  taken  regarding  heating   low-melt- 
itig  metals  in  a  platinum  vessel? 

6.  What  other  substances  also  injure  platinum  seriously? 

7.  In  what  way  have  you  seen  platinum  used  in  chemical  experi- 
ments?    Why  is  it  used  frequently  in  the  chemical  laboratory? 

8.  Name  some  other  valuable  uses  for  platinum  in  the  arts. 

9.  Why  should  platinum  not  be  used  for  jewelry? 

10.  Give  some  one  point  of  interest  about  osmium,  iridium  and 
palladium.     Give  some  use  for  iridium. 

11.  Where    does   palladium    belong    in    the    table?      What    other 
metals  are  associated  with  it? 


TABLES  FOR  REFERENCE  AND  GLOSSARY 


438  APPLIED    CHEMISTRY 

Solubilities  of  Common  Compounds 

It  may  be  desirable  to  know  at  times  whether  a  com- 
pound is  soluble  in  water.  A  few  general  rules  may  be 
helpful  and  are  given  below. 

(a)  All  salts  of  the  sodium  group,  including  those  of 
ammonium  are  soluble,  with   the   exception  of  two   or 
three  very  uncommon  ones. 

(b)  All  bromides  are   soluble   except   those   of  lead, 
mercury,  and  silver. 

(c)  All   carbonates   of   the   sodium   group,   including 
ammonium,  are  soluble;  all  others  are  insoluble. 

(d)  All  chlorates  are  soluble. 

(e)  All  chlorides  are  soluble  except  lead  chloride,  mer- 
curous  chloride,  and  silver  chloride. 

(f)  T.he  hydroxides  of  the  sodium  group,  ammonium, 
and  the  calcium  group  are  soluble,  calcium  only  moder- 
ately so,  while  all  others  are  insoluble. 

(g)  All  nitrates  are  soluble. 

(h)  The  oxides  of  the  sodium  and  calcium  group  are 
chemically  soluble  in  water,  that  is,  they  react  to  form 
a  new  compound,  the  hydroxide.  All  other  oxides  are 
insoluble  in  water. 

(i)  Phosphates  are  insoluble  except  those  of  the  al- 
kali metals  and  ammonium. 

(j)  Silicates  are  insoluble  except  those  of  the  alka- 
lies and  ammonium.  Even  then  if  mixed  with  silicates 
of  heavier  metals  they  are  insoluble. 

(k)  The  sulphates  of  barium,  calcium,  lead  and  stron- 
tium are  insoluble ;  others  are  soluble. 


TABLES    FOR    REFERENCE  439 


Some  Interesting  Temperatures 

Absolute  zero  -273°  C 

Hydrogen  melts  -200 

Hydrogen  boils  -252.6 

Nitrogen  melts  -21-4 

Nitrogen   boils  -194 

Oxygen  boils  -182.5 

Alcohol  freezes  -130 

Mercury  freezes  -  39.5 
Water  freezes  0 

Room  temperature  21 

Ether  boils  34.6 

Human  body  37 

Wood's  Metal  melts  60 

Alcohol  boils  78.5 

Water  boils  100 

Sulphur  melts  (rhomb)        114.5 
Tin  melts  232 

Lead  melts  327 

Mercury  boils  357 

Zinc  melts  419 

Dull  red  heat  650 

Aluminum   melts  6(50 

Bright  red  heat  1,000 
(Jold  melts                        '   1,064 

White  heat  1,350 

Iron  melts  1,520 

Platinum   melts  1,750 

Corundum  melts  2,000    (about) 

Oxyhydrogen  flame  2,500 

Oxyacetylene  flame  2,700 

Tungsten  melts  3,000 

Thermit  gives  3,500   (about) 

Electric   arc  4,000   (about) 


440  APPLIED    CHEMISTRY 

Tables  of  Weights  and  Measures 

WEIGHTS 

10  milligrams    (mg.)    =  1  centigram    (eg.) 
10  centigrams  =  1  decigram   (dg.) 

10  decigrams  =  1  gram   (g.) 

1,000  grams  =  1  kilogram    (kg.) 

ENGLISH  EQUIVALENTS 
1  kilogram          —    2.2046  pounds 
28.35  grams         =1  ounce 

1  gram  =  15.43  grains 

500  grams  =    1.1023  pounds 

The  unit  of  weight  in  the  Metric  System  is  the  gram. 

VOLUMES 

1,000  cubic  centimeters  (c.c.)  —  1  liter 
1  cubic  decimeter  (c.d.)  =  1  liter 
1  liter  (1.)  =1.056  liquid  quarts 

The  unit  in  the  Metric  System  is  the  liter. 

LENGTH 

10  millimeters   (mm.)  =  1  centimeter  (cm.) 
10  centimeters  =  1  .decimeter  (dm.) 

10  decimeters  =  1  meter  (m.) 

ENGLISH  EQUIVALENTS 
1  centimeter  =    0.3937  inches 

2.54  centimeters  =.    1.0  inch 

1  meter  =  39.37  inches 

THERMOMETER  EQUIVALENTS 

For  scientific  work  the  centigrade  thermometer  is  always  used 
and  readings  given  in  scientific  books  are  always  centigrade  unless 
otherwise  specified.  Freezing  water  is  0°  C.  and  boiling  point  is 
100°  C. 

0  Centigrade  is     32  Fahrenheit  and  273  Absolute 
100  "          "   212  "  "     373        " 

One  degree  Centigrade  —  %  of  a  degree  Fahrenheit 
One  degree  Fahrenheit  =%  of  a  degree  Centigrade 
One  degree  Centigrade   =  One  degree  Absolute 
To  convert  centigrade   degrees   into  Fahrenheit,  multiply  by  % 
and  add  32,  algebraically.     This  means  that  if  the  centigrade  read- 
ing is  below  zero,  it  would  have  the  minus  sign  and  one  would  be 


TABLES   FOR    REFERENCE 


441 


substracted  from  the  other.  To  convert  Fahrenheit  readings  into 
centigrade  multiply  by  %  after  substracting  32  from  the  Fahrenheit 
reading. 

LIST  OF  ELEMENTS,  THEIR  SYMBOLS  AND  ATOMIC  WEIGHTS.  (Cb=16.) 
(The  more  important  elements  are  printed  in  heavy  type.) 


NAME   OF 
ELEMENT 

SYM- 
BOL 

ATOMIC 
WEIGHT 

NAME   OF 
ELEMENT 

SYM- 
BOL 

ATOMIC 
WEIGHT 

Aluminum  
Antimony  
Argon.  . 

Al 
Sb 
A 

27.1 

120.2 
39.88 

Molybdenum.  . 
Neodymium  .  .  . 
Neon  

Mo 
Nd 

Ne 

96.0 

144.3 
20.2 

Arsenic     

As 

7496 

Nickel     .  .      .  . 

Ni 

58.68 

Barium 

Ba 

137  37 

Niton 

Nt 

222  4 

Bismuth  
Boron  

Bi 
B 

208.0 
110 

Nitrogen  
Osmium      .... 

N 
Os 

14.01 
190  9 

Bromine     .... 

Br 

79  92 

Oxvsen 

o 

16  00 

Cadmium 

Cd 

112  4 

Palladium 

Pd 

106  7 

Caesium 

Cs 

132  81 

Phosphorus.  .  .  . 

p 

31.04 

Calcium  

Ca 

40.07 

Platinum  

Pt 

195.2 

Carbon 

c 

12  00 

Potassium  

K 

39.1 

Cerium      

Ce 

140.25 

Praseodymium 

Pr 

140.6 

Chlorine 

Cl 

35  46 

Radium     

Ra 

2264 

Chromium 

Cr 

52  0 

Rhodium  

Eh 

102.9 

Cobalt     

Co 

58.97 

Rubidium  

Rb 

85.45 

Columbium.  .  .  . 

Cb 

Cu 

93.5 
63.57 

Ruthenium. 
Samarium  .... 

Ru 

Sa 

101.7 
150.4 

Dysprosium 

Dv 

162  5 

Scandium  

Ss 

44.1 

Erbium  

Er 

167.7 

Selenium  

S<? 

79.2 

Eu 

152  0 

Silicon  

Si 

28.3 

Fluorine 

F 

19  0 

Silver 

A? 

10788 

Gd 

157  3 

Sodium  

Na 

23.00 

Gallium 

Ga 

69  9 

Strontium  

Sr 

87.63 

GP 

72  5 

Sulphur 

g 

3207 

Glucinum      .  .    , 

Gl 

91 

Tantalum  

Ta 

181.5 

Gold 

An 

1Q7  o 

Tellurium      .  . 

Te 

127.5 

Helium        

He 

3  99 

Terbium  

Tl) 

159.2 

Holmium 

Ho 

163  5 

Thallium  

Tl 

204.0 

H  vdro  cr  en 

H 

1  008 

Thorium          .  . 

Th 

232.4 

Indium        

In 

114  8 

Thulium  

Tm 

168.5 

Iodine 

j 

j90  Q2 

Tin         

Sn 

119.0 

Iridium  

Ir 

193.1 

Titanium  

Ti 

48.1 

Iron 

Fe 

55  84 

Tungsten  

W 

184.0 

Krypton      .... 

Kr 

82.92 

Uranium  

U 

238.5 

La 

139  0 

Vanadium  

V 

51.0 

Lead 

Pb 

207  1 

Xenon  

Xe 

130.2 

Lithium  

Li 

6.94 

Ytterbium  .... 

Yb 

172.0 

Lu 

174  0 

Yttrium  

Yt 

89.0 

Magnesium 

Mff 

24  32 

Zinc  

Zn 

65.37 

Manganese  .... 
Mercury  

iri.^ 
Mn 
Hg 

54.93 
200.6 

Zirconium  .... 

Zr 

90.6 

442  APPLIED    CHEMISTRY 

Names  and  Formulas  of  the  More  Common  Chemicals 

Acetic  acid HC2H3O, 

Alcohol C2H5OH 

Alum,  ammonium    (NH4)2A12(SO4)4 

Alum,  potassium K2A1,(SO4)4 

Aluminum  oxide    A12OS 

Aluminum  sulphate- A12(SO4)3 

Ammonium   bicarbonate NH4HCCv. 

1 1  carbonate    (NH4),CO3 

1 1  chloride NH4C1 

' i  hydroxide    NH4OH 

' '  nitrate    NH4NOa 

' (  sulphate     (NH4)2SO4 

Antimony  oxychloride     SbOCl 

< '          trichloride    . .  SbCl3 

' '          trisulphide   '. .  SbaS3 

Arsenic   trioxide    As2O3 

Barium  carbonate    BaCO3 

1 '         chloride     BaCl2 

1 '        dioxide BaO2 

' <        hydroxide Ba(OH)2 

' '         nitrate Ba(NO3)_, 

* '        oxide     BaO 

' '         sulphate    BaSO4 

Bismuth  chloride BiCl3 

' '         nitrate    Bi(NO3)3 

"         subnitrate .  BiONO3 

' '         trioxide Bi2O3 

Bleaching  powder    CaCl(OCl) 

Borax Na2B4O7 

Calcium  carbide     CaC2 

1 '         carbonate CaCO3 

chloride    CaCl2 

( '        fluoride CaF2 

"         hydroxide     Ca(OH)2 

' '        oxide  (lime)    CaO 

1 '        phosphate Ca3(PO4)2 

' '        sulphate CaSO4 

Carbolic  acid C6H5OH 

Carbon  disulphide CS2 


TABLES    FOR    REFERENCE  44)  J 

Chloroform CIICI, 

Chrome    yellow    PbCrO4 

Cinnabar HgS 

Copper  acetate  Cu(C2H3O2), 

' '        cliloride CuCl, 

"        nitrate Cu(NO3), 

< '        oxide CuO 

* '        sulphate     CuSO4 

1 '        sulphide CuS 

Ether,  sulphuric (C,H5),O 

Ferric  chloride   Fe2Cl6 

1 '       hydroxide Fe2(OH)6 

' '       nitrate   Fe,(NO3)0 

' '       oxide    Fe2O3 

Ferrous  sulphate FeS04 

Ferrous  sulphide    FeS 

Fluor  spar    CaF2 

Gold  trichloride AuCl3 

Hydrochloric  acid HC1 

Hydrofluoric  acid    HF 

Hydrogen  peroxide H.O., 

Hydrogen  sulphide    H.,8 

Hypochlorous   acid    HC1O 

lodic  acid HIO3 

lodof  orm     CHI3 

Lead  acetate Pb(C2H3O,), 

' '      carbonate    PbCO3 

' '     chloride PbCl2 

1 '      chromate   PbCrO4 

' '     nitrate Pb(NO3)2 

' '      oxide    (litharge)    PbO 

'  <     sulphate     PbSO4 

Lime : CaO 

Litharge    PbO 

Lithium  chloride   - LiCl 

Magnesia MgO 

Magnesium  carbonate MgCO3 

' '  chloride    MgCl2 

'  <  oxide    MgO 

'  <  sulphate     MgSO4 

Manganese  dioxide MnO, 


444  APPLIED    CHEMISTRY 

Mercuric  chloride HgCl0 

' '         iodide    HgI2 

' '         nitrate Hg(NO8)2 

' '         oxide HgO 

' '          sulphide    HgS 

Mercurous  chloride    Hg2Cl2 

' '  iodide     Hg J., 

nitrate Hg"2(NO8)2 

Minium    PbsO4 

Phosphine .  PH3 

Phosphorus  pentoxide P2O5 

Plaster  of  Paris    CaSO4,H2O 

Platinum  tetrachloride PtCl4 

Potassium  acetate KC2H3O.( 

' '          bicarbonate    KHCO3 

' '          bromide    KBr 

' '  carbonate    K,CO3 

' '  chlorate    KC1O3 

' '          chloride    KC1 

' l          chromate    K2CrO4 

"          cyapide     KCN 

' '          dichromate     K2Cr,07 

' '          ferricyanide     K3Fe(CN)fl 

1 '  ferrocyanide .  K4Fe(CN)6 

"          hydroxide     KOH 

' '          iodide    KI 

' '  nitrate     KNO3 

' '  nitrite   KNO, 

' '  permanganate    KMnO4 

4 '          sulphate    K,SO4 

sulphocyanate KSCN 

Silica    SiO2 

Silver  bromide AgBr 

' '       chloride    AgCl 

' '      iodide Agl 

' '       nitrate   AgNO3 

Sodium  acetate NaC2H3O2 

1 '        arseniate   Na3AsO4 

' '       arsenite NaAsO3 

' '        bicarbonate     NaHCO3 

' '       carbonate Na2C03 


TABLES   FOR    REFERENCE  445 

Sodium  chloride     NaCl 

hydroxide    NaOH 

' '        iodide     Nal 

' '        nitrate   NaNO3 

' '        nitrite NaNO2 

' '        phosphate    Na2HPO4 

'  *        sulphate     Na2SO4 

' l        sulphide Na2S 

* '        sulphite Na2SOs 

' '        thiosulphate    Na2S2O3 

Stannic  chloride     SnCl4 

' '         oxide SnO, 

Stannous  chloride SnCl, 

Strontium  nitrate    Sr(NO3)2 

Sulphur  dioxide   SO2 

Sulphuric  acid H2SO4 

Sulphurous   acid    H,SO3 

Sulphur  trioxide    SO3 

Zinc  chloride ZnCl2 

' '      oxide     ZnO 

' «      sulphate ZnSO4 


GLOSSARY 
Chemical  Terms 

Actinic.  Actinic  light  rays  are  those  which  have  the  power  of 
producing  chemical  change  in  substances,  as  upon  a  photo- 
graphic plate. 

Alkali.  A  soluble  hydroxide,  with  caustic  properties,  sharp  bit- 
ing taste,  and  power  of  corroding  the,  skin. 

Allotropic.  Literally,  another  form  of  an  element;  more  often 
applied  to  the  unusual  form.  Ozone  as  related  to  oxygen. 

Alloy.  A  mixture  of  two  or  more  metals,  melted  together  so  as 
to  be  homogeneous.  Example,  brass. 

Amalgam.     An  alloy,  one  component  of  which  is  mercury. 

Amorphous.     Without  special  form;  uncrystallized. 

Anesthetic.     A  substance  used  to  produce  unconsciousness. 

Anhydride.  An  acidic  oxide.  An  oxide  forming  an  acid  on  the 
addition  of  water. 

Anhydrous.     Without  water. 

Antiseptic.  An  antiseptic  is  a  substance  used  to  prevent  decay 
or  destroy  pathogenic  bacteria. 

Basic.     Having  the  properties  of  a  base  or  alkali. 

Binary.     A  compound  consisting  of  two  elements. 

Calcine.     To  heat  strongly. 

Commercial.  A  term  applied,  to  chemicals  not  pure  but  suffi- 
ciently so  for  all  ordinary  uses. 

C.  P.  Chemically  pure.  Applied  to  a  better  grade  of  chemicals 
than  those  marked  "commercial." 

Decant.     To  pour  off  a  liquid  from  a  precipitate. 

Deliquesce.     To  gather  moisture  from  the  air  and  become  liquid. 

Desiccator.     A  vessel  used  for  drying  substances. 

Destructive  Distillation.  Heating  a  substance  in  a  closed  re- 
tort so  as  to  decompose  it  and  produce  new  substances;  as 
in  distilling  coal. 

Downward  Displacement.  Collecting  a  gas  heavier  than  air  by 
letting  it  flow  downward  into  a  bottle  full  of  air,  thus  dis- 
placing the  air. 

Distillate.     The  liquid  obtained  by  distillation. 

446 


GLOSSARY  447 

Dyad.     An  element  with  valence  of  two. 

Effloresce.  To  give  up  water  of  combination  at  room  temper- 
ature and  become  a  powder. 

Electrode.     The  terminal  of  a  battery. 

Empirical.  Applied  to  a  formula  which  shows  composition  only. 
Xot  structural. 

Escharotic.     A  caustic.     A  substance  which   corrodes. 

Filtrate.     The  liquid  which  passes  through  a  filter. 

Flocculent.     Flaky;  often  applied  to  certain  precipitates. 

Flux.  A  substance  used  to  lower  the  melting  point  of  some  sub- 
stance: often  it  is  a  solvent  for  the  substance. 

Fractional  Distillation.  Boiling  a  liquid  and  separating  it  into 
portions  or  fractions  by  means  of  their  difference  in  boiling 
points. 

Gelatinous.  Jelly-like  or  starch-like  paste;  applied  to  precipi- 
tates. 

Germicide.     A  substance  destructive  of  germs. 

Gravimetric.     Applied  to   determining  the  proportion  by  iccicjJit. 

Halogens.     Literally,  salt  producers;  the  chlorine  family. 

Hydrated.     Containing  water. 

Hydroxyl.     The  group  HO,  found  in  all  hydroxides. 

Hygroscopic.  Having  the  property  of  becoming  moist  in  dam}) 
air. 

Indicator.  A  substance,  like  litmus  paper,  used  to  determine 
when  a  reaction  has  been  completed. 

Ion.  An  electrically  charged  atom  or  group  of  atoms.  They 
may  be  either  positive,  called  cations;  or  negative,  called  amons. 

Isomeric.  Two  compounds  are  isom.cric  when  they  have  the 
same  percentage  composition,  the  same  empirical  formula, 
but  are  entirely  different  in  properties. 

Monad.     An  element  with  a  valence  of  one. 

Monobasic.  Applied  to  an  acid  having  only  one  displaceable 
atom  of  hydrogen  in  a  molecule,  as  hydrochloric  acid. 

Mordant.     Something  used  to  set  the  color  or  dye  in  cloth. 

Nascent.  Literally,  bring  set  free  •  applied  to  a  gas  as  it  is  be- 
ing set  free  from  some  compound;  in  the  atomic  form  and 
very  active,  chemically. 

Neutral.     Neither  acid  nor  alkaline  in  character. 

Neutralization.  The  process  of  combining  an  acid  and  a  base  so 
as  to  exactly  destroy  the  properties  of  each  and  form  a  new 
compound. 


448  APPLIED    CHEMISTRY 

Nitrogenous.     Containing  nitrogen. 

Occlude.  To  condense  within  the  pores  of  a  metal;  as  hydrogen 
in  platinum  or  carbon  monoxide  in  hot  cast  iron. 

Oxidation.  The  combining  of  a  substance  with  oxygen.  In  a 
broader  sense,  raising  the  valence  of  an  element. 

Oxidizing  Agent.  A  substance  which  will  bring  about  oxidation. 
Usually  a  substance  containing  oxygen,  with  which  it  will 
part  readily.  Often  chlorine  or  bromine. 

Paste.  A  very  pure  form  of  flint  glass  used  in  making  imitation 
diamonds. 

Pneumatic.     Term  applied  to  the  trough  used  in  collecting  gases. 

Polymer.  A  term  applied  to  one  compound  the  multiple  of  an- 
other. Thus,  C6H6  is  a  polymer  of  C2H2. 

Precipitate.  A  solid  thrown  out  in  a  solution;  it  may  be  a 
mere  cloud  or  so  very  dense  and  heavy  as  to  settle  very 
rapidly. 

Radical.  A  group  of  atoms  which  act  chemically  as  if  a  single 
element. 

Reaction.  The  chemical  change  taking  place  between  two  or 
more  substances. 

Reagent.     A  substance  used  in  a  chemical  reaction. 

Roast.     To  heat  strongly  in  presence  of  air;  hence  to  oxidize. 

Saturated.     Fully  satisfied.     Containing  all  possible. 

Slag.  A  nearly  black  glass  formed  in  blast  furnaces  in  the  re- 
duction of  iron  and  other  metals. 

Sublimate.     The  substance  obtained  by  sublimation. 

Sublimation.  The  process  of  vaporizing  a  solid  which  boils  with- 
out melting,  and  collecting  the  vapors. 

Supernatant.  Overlying.  Said  of  a  liquid  above  a  precipitate 
which  has  settled. 

Ternary.     Composed  of  three  elements  or  more. 

Upward  Displacement.  Method  of  collecting  light  gases  by  let- 
ting them  flow  upward  into  a  bottle  of  air,  displacing  the 
air. 

Volatile.  A  term  applied  to  substances  which  readily  change  in- 
to gas. 

Volumetric.  Estimation  of  quantity  by  measuring  the  volume, 
not  weight. 


GLOSSARY  449 

Common  or  Commercial  Names 

Agate.  A  species  of  quartz,  often  beautifully  colored  in  con- 
centric rings. 

Alabaster.  A  beautiful  white  or  delicately  tinted  form  of  gyp- 
sum. 

Alum.  A  double  sulphate,  containing  a  univalent  and  a  triva- 
lent  metal.  Common  alum  is  potassium  aluminum  sulphate. 

Alumina.     Aluminum  oxide. 

Amethyst.     A  variety  of  quartz,  pale  violet  in  color. 

Antichlor.  A  substance  employed  to  neutralize  the  chlorine  used 
in  bleaching.  It  is  generally  sodium  thiosulphate. 

Arsenic.     The     usual     commercial     name     for     arsenic     trioxide. 

Arsenous  Acid.  A  term  often  applied  to  arsenic  trioxide.  Strict- 
ly speaking  arsenous  acid  is  H3AsO3. 

Arsine.  Hydrogen  arsenide  also  called  arseniuretted  hydrogen, 
H3As. 

Baryta.     Barium  oxide,  BaO. 

Baryta  Water.     Barium  hydroxide,  Ba(HO)2. 

Bauxite.     Hydrated  aluminum  oxide,  A12O3:H2O. 

Benzene.  More  properly  called  benzol,  C6H6,  obtained  from 
coal  tar. 

Benzine.  A  light  oil  resembling  ordinary  gasoline,  obtained  from 
petroleum. 

Bicarbonate  of  Soda.     Cooking  soda,  NaHCO3. 

Bituminous.     Containing  bitumen  or  oil. 

Blanc  de  fard.     Bismuth  oxynitrate,  BiONO3. 

Blue  Vitriol.     Copper  sulphate  crystals. 

Borax.     Sodium  tetraborate. 

Butter  of  Antimony.  Antimony  chloride,  so  called  from  its  yel- 
low color. 

Calcite.  Crystallized  calcium  carbonate,  being  three  in  scale  of 
hardness. 

Calomel.     Mercurous  chloride,  Hg2Cl,. 

Carborundum.     Silicon  carbide,  SiC,used  as  an  abrasive. 

Caustic  Potash.     Potassium  hydroxide. 

Caustic  Soda.     Sodium  hydroxide. 

Chalcedony.     A  variety  of  quartz. 

Chalk.     A  soft,  natural  form  of  calcium  carbonate. 

Chloride  of  Lime.     Commercial  name  for  bleaching  powder. 

Chrome  Alum.     A  double   sulphate  of  potassium  and  chromium. 


450  APPLIED    CHEMISTRY 

Chrome  Yellow.     Lead  chromate,  PbCrO4. 

Copperas.     Ferrous  sulphate,  green  vitriol. 

Corrosive  Sublimate.     Mercuric  chloride,  HgCl2. 

Corundum.     Native,  uncrystallized  aluminum  oxide,  nine  in  scale 

of  hardness. 

Emerald.     Aluminum  oxide,  crystallized,  green  in  color. 
Emery.     An  impure,  native  form  of  aluminum  oxide. 
Epsom  Salts.     Crystallized  magnesium  sulphate. 
Felspar.     A  complicated  silicate  rock,  which,  decomposed,  forms 

clay. 

Fool's  Gold.     Iron  pyrites,  FeS2. 
.  Fuller's  Earth.     A  white  variety  of  clay. 
Green  Vitriol.     Ferrous  sulphate. 
Gypsum.     Native  calcium  sulphate,  CaSO4:2H2O. 
Hartshorn.     An  old  name  for  ammonia,  so  called  because  made 

from  the  horns  of  deer. 
Hypo.     Sodium  thiosulphate,  used  in  photography  as  fixing  bath 

and  as  an  antichlor. 
Iceland    Spar.     A    transparent,    crystallized    variety    of    calcium 

carbonate. 
Jeweler's  Rouge.     Ferric  oxide,  native,  used  in  polishing  and  as 

a  paint. 
Kelp.     A  variety  of  seaweed.     Also  applied  to  the  ashes  derived 

by  burning  the  seaweed. 

Labarraque's  Solution.     Sodium  hypochlorite,  NaClO. 
Lac  Sulphuris.     A  fine  white  precipitate  of  sulphur  in  limewater. 
Laughing  Gas.     Nitrous  oxide  N2O. 
Lime.     Calcium  oxide. 

Limestone.     Native  calcium  carbonate,  uncrystallized. 
Limewater.     Calcium  hydroxide  solution. 
Lunar   Caustic.     Silver   nitrate   in   stick   form    containing    small 

percentage  of  silver  chloride. 
Magnesia.     Magnesium  oxide. 
Marble.     Crystallized  limestone. 
Milk   of  Lime.     Calcium   hydroxide   solution   containing  lime   in 

suspension. 

Minium.     Eed  Lead,  Pb3O4. 

Naphtha.     A  low  boiling  gasoline  obtained  from  petroleum. 
Nitre.     Potassium  nitrate. 

Nordhausen's  Acid.     Fuming  sulphuric,  H2S2Or 
Oil  of  Vitriol.     Sulphuric  acid. 


GLOSSARY  451 

Opal.     A  variety  of  silica. 

Paris  Green.     Copper  aceto-arsenite. 

Pearl  Ash.     Pure  potassium  carbonate. 

Plaster  of  Paris.     Monohydrated  calcium  sulphate,  CaSO4:H2O. 
Plastic  Sulphur.     Amorphous  sulphur,  prepared  by  pouring  boil- 
ing sulphur  into  cold  water. 

Potash.     Commercial  potassium   carbonate. 

Powder  of  Algaroth.     Impure  antimony  oxychloride. 

Purple  of  Cassius.  A  purplish  colored  compound  obtained  by 
adding  to  a  solution  of  gold  chloride  a  small  amount  of 
stannous  and  stannic  chloride. 

Pyrites.  Usually  means  iron  pyrites,  FeS2.  There  is  also  a  copper 
pyrites. 

Quicklime.     Lime. 

Red  Precipitate.     Mercuric  Oxide. 

Sal  Ammoniac.     Ammonium  chloride. 

Sal  Soda.     Crystallized  sodium  carbonate. 

Salt  Cake.  Sodium  sulphate  as  obtained  in  the  Leblanc  proc- 
ess of  making  sal  soda. 

Saltpeter.     Potassium  nitrate. 

Scheele's  Green.     Acid  copper  arsenite,  CuHAsO3. 

Silica.     Silicon  dioxide. 

Slaked  Lime.  Calcium  hydroxide,  formed  by  adding  water  to 
lime. 

Smoky  Quartz.  A  variety  of  quartz;  silica,  brown  in  color,  some- 
times almost  black. 

Soda.  Usually  cooking  soda  is  meant.  Sodium  bicarbonate, 
XaHCO3. 

Sutmitrate  Bismuth.  Bismuth  oxynitrate,  often  sold  as  "  bis- 
muth." BiONO.,. 

Sugar  of  Lead.     Lead  acetate,  Pb(C2H3O2)2:3H2O. 

Vermilion.     Artificial  mercuric  sulphide. 

Whito  Arsenic.     Arsenic  trioxide. 

White  Lead.     Basic  lead  carbonate;  a  common  white  pigment. 

White  Vitriol.     Crystallized  zinc  sulphate.     ZnSO4:7H2O. 

Zinc  White.     Zinc  oxide,  ZnO.     A  common  white  pigment. 


INDEX 


Absolute  zero,   85 
Acetylene,   183,   200 

welding',  185 
Acids,   137 

nomenclature  of,  139 

organic,  208 

strong  and  weak,  246 
After-damp,  171 
Agate,  294: 
Air,   a   mixture,   73 

composition  of,  73 

early  ideas   of,   72 

liquid,   80 

pressure  of,  89 

value   of   constituents,   75 
Alabastine,  337 
Alcohols,  206 

denatured,  207 

methyl,    207 

wood,    207 
Aldehydes,   209 
Alkali  earths,  336 
Alkali  metals,   305 
Alkalies,   138 
Allotrope,  58 
Alum,  399 

Alumina tes,  395,  400 
Aluminum,    abundance,    392 

alloys  of,   398 

bronze,   398 

characteristics,  394 

hydroxide,    399 

preparation,   393 

uses,  395 
Amines,   230 
Ammonia,   147 

characteristics  of,   148 

commercial  supply,   147 

uses  of,  148 
Amylene,   217 
Anhydride,  137 


Anode,  29 
Antichlor,  263 
Antimony,  286 

chloride,   287 

sulphide,  288 

uses,   of,  148 
Aqueous  tension,  91 

table  of,  92 
Argon,  81 
Arsenic,  282 

oxides,  284 

poisoning  by,  285 
Arsine,  282 
Asbestos,  380 
Aspirin,   187 
Atomic   weights,   99 
Atoms,  97 

number  in  molecule,  101 

theory  of,  97,  99 
Avogadro's  hypothesis,   100 
Azurite,   364 


P, 


Babbitt  metal,  287 
Baking  powders,  328 

alum,  329 

healthfulness  of,  331 

phosphate,  329 

tartrate,  329 
Ballistite,   156 
Barium,  343,  344 
Barometer,   aneroid,   88 

mercurial,   89 
Bases,  138 

nomenclature  of,  138 

strong  and  weak,   246 
Basic  Lining  Process,  426 
Bauxite,  394 
Beet   sugar,   221 
Benzine,  166 
Biscuits,  beaten,  334 


453 


454 


INDEX 


Bismuth,  288 

compounds,    290 
Black  damp,  171 
Blast  furnace,  420 
Blast  lamp,  195 
Blau  gas,  185 

Blow  pipe,  oxyhydrogen,  195 
Blue  prints,  373 
Blue  stone,  366 
Blue  vitriol,  366 
Bohemian   glass,   299 
Bone  black,  167 
Borax,  320 
Boyle,  Eobert,  25 
Boyle's  LaAv,  87 
Bread,  aerated,  334 
Brittani,   287 
Bromine,  129 

characteristics,    130 

preparation  of,   129 

uses,  131 
Bronze,  404 
Bunsen  burner,   194 

application  of,  194 
Butane,  204 
Butylene,  217 
Butyrin,  213 


Cadmeia,  24 
Calcium,  336 

characteristics,  337 
chloride,   342 
light,  68,  201 
Candles,  197 
Cane  sugar,  220 
Carbohydrates,  219 
Carbolic  acid,  187 
Carbona,  175 
Carbon    dioxide,   characteristics 

of,  172 
cycle,  78 
in  air,  78,  171 
preparation,   171 
test  for,  175 
uses,  173 
Carbon,  forms  of,  160 

occurrence,  159 
Carbon  monoxide,  168 
characteristics.  170 


Carbon  tetrachloride,  355 
Carborundum,  176 
Castner  Process,  307 
Catalysis,  52 
Cathode,  29 
Cations,   242 
Celluloid,   156 
Celulose,  222,  226 
Cement,  340 

hydraulic,  341 

natural,  340 

Portland,  340 
Chalcedony,  294 
Chalk,  337,  342 
Charcoal,  166 
Charles'  Law,   85,   86 
Chemical  changes,   30 
Chemical  union,  26 
Chile  saltpeter,  306 
Chlorination  process,   375 
Chlorine,       characteristics       of, 
122,  123 

discovery  of,   120 

preparation,  120,  121 

uses,  124 
Chrome  steel,  428 
Chromium,  411 

characteristics,  411 

compounds,  412 

preparation,  411 

uses,  411 
Cider,  hard,  209 
Cleaning,  dry  methods,  355 
Coal,  163 

varieties,  164 
Cobalt,   419,   432 

barometer,  432 
Coke,  168 
Collodion,   156 

Combustion,    definition    of,    56, 
190 

old  theory,  69 

problems  in,  114 

spontaneous,  56 
Compounds,  binary,  14 

definition  of,  26 

general  plan  of  naming,  27 

percentage  composition,  114 

organic,  160,  203 

ternary,  181 


INDEX 


455 


Compounds — Gout  'd — 

unsaturated,  179 
Concrete,  341 

Conductivity    of    solutions,    239 
Converter,  425 
Copper,   characteristics,   364 

electrolytic,    367 

occurrence,   363 

uses,  365 
Copper  acetate,  368 

chloride,  368 

oxides,  368 

sulphate,  368 
Copperas,   429 
Coquina,    336 
Cordite,  156 
Corpuscles,  99 
Corpuscular   theory,   99 
Corrosive  sublimate,  389 
Corundum,  393 
Cracking  oils,  166 
Crisc.o,    219 
Crown   glass,   299 
Cryolite,  393 
C.   T.   S.,  399 
Cyanide  process,   375 

D 

Deliquescence,  43 
Dewar  bulbs,  81 
Dextrine,  222 
Diads,  179 
Diamonds,  161 

artificial,   162 

composition  of,   161 

origin,  161 

uses,    162 
Diastase,  207 
Diffusion  of  gases,  14,  96 
Disaccharids,    219,   220 
Dissociation,  240 

by  solution,  241 
Distillation,  fractional,  165 
Dog  tooth  spar,  337 
Double   decomposition,   31 
Drummond  Light,  68,  201 
Dutch  cleanser,   295 


E 

Efflorescence,  41 

Egg  preserving,  297 

Electrolytes,   239 

Electromotive  series,  65 

Electrons,   99 

Electrotypes,  366 

Elements,   classification  of,  265 

definition   of,   25 

most  abundant,  26 

number,  25 

union  of,  28 
Emeralds,  393 
Emulsions,  353 
Enzymes,   224 
Equations,   109 

uses  of,  112 
Esters,    212 
Ethane,   204 
Ether,    ethyl,    210 
Ethereal  salts,  212 
Ethyl  butyrate,   212 
Ethylene,  217 


Fats,  as  foods,  227 

composition   of,   216 
Feldspar,   295 
Ferric  compounds,  429 
Ferrous     ammonium     sulphate, 

429 

Ferrous  sulphate,   429 
Fertilizers,  281 
Fiber  silk,  156 
Firedamp,   204 

Fire  extinguisher,  Babcock,  174 
Flame,  189 
Flame,  candle,  193 

chemical  action  in,  190 

structure   of,    191 
Flash  point,  198 
Flint,  294 
Flint  glass,  300 
Foods,  kinds  of,  224 

mineral,  230 

tables,  228,  229,  231,  232 
Fools'  gold,  420 
Formaldehyde,  209 


456 


INDEX 


Formic  acid,  208 
Formulas,  107 

determination  of,   116 

structural,  108 
Freezing    point    lowering,    235, 

236 
Fulminating  mercury,  154 


Galvanized  iron,  384 
Gangue,  422 
Ganister,  425 
Gas  carbon,  168 

coal,  186 

laws,  85,  87 

illuminating,  199 

liquor,  148 

natural,  166,  183 

pressures,  cause  of,  97 
problems  in,   89,  90 

water,   187 

weight  of  liter  of,  115 
Gasoline,  165,  205 
German  silver,  384 
Glass,   annealing  of,   303 
Glass  manufacture  of,  300,  301, 

302 

Glucose,  219 
Gluten,   327 
Glycerine,  213,  318 
Glycerol,   213 
Glyceryl  esters,  213 
Glycogen,  225 
Gold,  characteristics  of,  376 

leaf,  376 

mining,  374 

occurrence,   374 
Gram   molecule,  104 
Granite  ware,  432 
Graphite,  160,  163 
Grids,   408 
Grits,  341 
Green  vitriol,  429 
Gunpowder,  153 
Gypsum,  337 


IT 


Halogens,  119 


Hardness,  degrees  of,  351 

effect  on  soap,  350 
Hartshorn,  147 
Helium,  82 
Hematite,  420 
Hexane,  204 
Hoffmann  apparatus,  37 
Hydrates,    40 
Hydrocarbons,   203 
Hydrochloric  acid,   126 

characteristics  of,  127 

uses,  127 

Hydrofluoric  acid,  128 
Hydrogen,     characteristics     of, 
67 

discovery  of,  63 

occurrence,  63 

preparation  from  acids,    66 

preparation  from  oils,   66 

preparation  from  water,  64 

uses,  68,  69 
Hydrogen   chloride,    125 

peroxide,  48 

phosphide,  279 

sulphide,  254 
Hydrogenatipn,  218 
Hydrolysis,  299,  313 
Hydroquinone,  187 
Hydrosulphuric   acid,  254 
Hydroxides,  138 
Hygroscopic   substances,   43 
Hypo,  263,  372 


Ice  manufacture,  149 
Infusorial  earth,  275 
Ink  stains,  355 
Inversion,  224 
Iodine,   131 

characteristics,   132,   133 

preparation,   132 

uses,  134 
Ions,  242 

Ions  and  valence,  243 
Iridium,   436 
Iron,  characteristics,  428 

compounds  of,  429 

oxidation  and  reduction  of, 
430 


INDEX 


457 


Iron — Cont  'd 
occurrence,  420 
passive  state,  428 
pig,  422 

reduction  of,  420 
wrought,  424 
Iron  carbide,   427 
Iron  carbonate,  420 
Isinglass,  295 
Isomorphous,   399 
Ivory  black,  167 
Ivy  poisoning,  407 


Jasper,  294 


K 


Kaolin,   295 
Kerosene,   165,    205 
Kieselguhr,  154 
Kindling  temperature,  57 


Lakes,  400 

Lamp,  carbon,  199 

kerosene,  197 

safety,   205 

tungsten,  201 
Lampblack,  469 
Lard,  artificial,  216 

compound,  216 
Lavoisier,    69 

Laws,  attraction  and  repulsion, 
29 

Boyle's,  87 

Charles',  85,  86 

definite  proportions,  40 

Gay-Lussac's,  103 

Henry's,  173 

multiple  proportions,  49 
Lea'd,  characteristics,  405 

family,  402 

occurrence,  405 

uses,  406 
Lead  acetate,  406 

carbonate,  407 

chloride,  408 

chromate,  408 

nitrate,  408 


Lead — Cont  'd 

oxides,  406 

pencils,  163 

sulphate,  408 
Leavening  agents,  327 
Lighting,  electric  methods,  199r 
201 

primitive  methods,  197 
Lime,  337 

uses,  338,   339 
Limonite,  420 
Litharge,  406 
Lubricating  oil,  165 
Lye,  316 


M 


Magnalium,  381,  398 
Magnesium,  characteristics,  380- 

compounds,  380 

family,  379 

uses,  381 

oxide,  381 

sulphate,  382 
Magnetic  oxide,  420 
Malachite,  364 
Manganates,  417 
Manganese,  416 

oxides,  416 

salts,  417 

steel,  428 
Manometer,  42 
Marble,  337 
Marsh's  test,  284 
Matches,  278 
Matter,  definition  of,  25 

kinds  of,  25 

present  theory  of,  25 

states  of,  84 
Mazola,  214 
Meerschaum,  380 
Mercuric  chloride,  389 

oxide,  388 

sulphide,  389 
Mercurous  chloride,  388 
Mercury,   characteristics,   386" 

occurrence,  386 

uses,  387 

Metals,  cleaning  of,  357 
Metathesis,  31 


458 


INDEX 


Meteorites,  420 
Methane,  204 

derivatives  of,  206 
Methylated  spirits,  207 
Mica,  295,  392 
Minium,  406 
Mixtures,  31 
Moisture  in  air,  79 
Molar  weight,  104 
Molecular  theory,  95 

weights,  100 

determination   of,   103 
Molecules,    definition  of,  95 

motion  of,  96 
Molybdenum,  411 
Monads,  178 
Monosaccharids,  219 
Mordants,  384 
Mucilage,  222 

N 

Naphtha,   166 
Nascent  condition,   283 
Negative,  photographic,  371 
Neutralization,  139 
Nickel,  419 

ammonium  sulphate,  431 

characteristics,   431 

compounds,  432 

steel,  428 

Nitric  acid,  151,  152,  153 
Nitrocellulose,   155 
Nitrogen,  characteristics  of,  147 

compounds,  291 

cycle,  77 

family,  275 

occurrence,  145 

preparation,  146 

value  of,  76 

Nitrogen-fixing  bacteria,   77 
Nitrogen  oxides,   150 
Nitroglycerine,  154 
Nitrous   oxide,   150,   151 
Noble  metals,  363 
Nonelectrolytes,  239 

O 

Ochre,  yellow,  431 
Oils,  as  foods,  227 
Olefins,  217 


Olein,  213 
Oleomargarine,  214 
Onyx,  294 
Oxidation,  56 
Oxides,  acidic,  137 

basic,  137 

definition  of,  136 
Oxygen,  abundance  of,  51 

characteristics  of,   54,  55 

discovery,  51 

preparation,  52,  53 

uses,  55 
Ozone,  characteristics,  60 

preparation,  58 

uses,  60 


Paint,  removal  of,  356 

Palladium,  434 

Papers,  photographic,  372 

Paraffin,  165 

Paris  green,  286 

Pectin,  226 

Pentads,  179 

Pentane,  204 

Periodic  system,  266 

Periodic  Table,  268 

Permanent  hardness,   346,  349 

Permanganates,  417 

Permutit  system,  349 

Petrified  forests,  295 

wood,  294 
Petroleum,  164 

by-products,  165 

kinds  of,  165 
Petroleum  ether,   165 
Pewter,  287 
Phenol,  187 
PMogiston,  69 
Phosphates,  281 
Phosphine,  279 

P  h  o  s  p  horus,     characteristics, 
276,  277 

discovery,  275 

forms  of,  276 

preparation,  275 

uses,  277 

Phosphorus  oxides,  280 
Picric  acid,  157 


1NDKX 


459 


Pig  iron,  422 
Pintsch  gas,  185 
Plaster,   land,    340 
Plaster  of  paris,  239 
Platinum,  434,  435 
Polishing  metals,  359 
Polysaccharids,   219 
Potassium,   321 
Potassium   bromide,   324 

carbonate,    322 

chlorate,  324 

cyanide,  325 

ferricyanate,  431 

ferrocyanate,  430 

hydroxide,   323 

iodide,  324 

nitrate,  323 
Potash,  322 

Powders,  smokeless,  156 
Prestolite,  184 
Propane,  204 
Propylene,  217 
Proteins.  227 
Ptomains,  230 
Pumice  stone,  295 
Pyrene,  175 


•Quartz,   295 


Q 


E 


Radicals,  108 
Reactions,  additive,   30 
completed,  244,  246 
Red  lead,  406 
Rhigoline,  166 
Rock  oil,  164 
Rose's  metal,   289 
Rouge,  431 
Ruby,  393 

S 

Salivation,  389 
Saltpeter,  324 
Saltrising  bread,  333 
Salts,  acid,  141 
binary,  142 


Salts — Cont  'd 

classes,  140 

definition,   140 

nomenclature,  141 
Sandstone,  294 
Saponification,   318 
Sapphire,   393 
Scale,  boiler,  347 
Siderite,  420 

Siemens-Martin  Process,  426 
Sienna,  burnt,  431 

raw,  431 
Silica,  296 
Silicic  acid,  296 
Silicon,  294 

dioxide,  296 
Silver,  characteristics,   368 

occurrence,  368 

sterling,  369 
Silver  bromide,  370 

chloride,   370 

nitrate,  369 

Simple  decomposition,  30 
Slag,  422 
Smalt,  432 
Soap,  317 

cleansing,  by,  354 

fillers,  319 

Soda,  cooking,  311,  327 
Soda  water,  173 
Sodium,      characteristics,      308, 
309,  310,  311 

family,  305 
Sodium  bicarbonate,  311 

carbonate,  312,  316 

chloride,   306 

hydroxide,  316,  317 

nitrate,  320 
Solder,  414 
Solution,  characteristics  of,  234 

concentration  of,  234 

definition,  233 
Solute,  233 
Solvay  process,  311 
Solvent,  233 
Spiegel,  426 
Stamp  mill,  376 
Starch,  219,  221 
Stearin,  213 


460 


INDEX 


Steel,  424 

Bessemer,  425 

cast,  425 

cementation  process,  424 

characteristics,  427 

kinds  of,  428 

open  hearth  process,  426 

tempering,  427 
Stibine,  287 
Storage  battery,  408 
Strontium,  343 
Sugar,  beet,  221 

cane,  220 

invert,  224 

of  lead,  406 
Suint,  323 
Sulphur,   characteristics,   251 

dioxide,  225 

occurrence,  249 

preparation,  250 

trioxide,  259 

uses,  253 
Sulphuric  acid,  259 

characteristics,    262 
manufacture  of,  259,  261 
uses,  263 

Sulphurous  acid,  259 
Superphosphate,  281 
Symbols,  106 
Sympathetic  ink,  432 
Synthetic  stones,  393 


T 


Tar,  186 

Tartar  emetic,  288 
Temporary  hardness,  346,  348 
Tetrads,  179 
Thermit,  397 
Thiosulphuric  acid,  263 
Thomas-Gilchrist   process,   426 
Tin,  alloys,  404 

characteristics,  403 

occurrence,  403 

oxides,  405 

plate,  403 

uses,  403 
T.  N.  T.,  157 
Transmutation  of  metals,  24 


Triads,  179 
Tungsten,  411,  414 
Tuyeres,  422 
Type  metal,  287 

U 

Univalence,  178 
Umber,   burnt,  431 

raw,  431 
Uranium,  411,  414 


Valence,  178 

in  ternary  compounds,  181 

variation  of,  179 
Vapor  pressure  lowering,  235 
Vaseline,  165 
Venetian  red,  431 
Ventilation,  76 
Vermilion,  389 
Vulcanite,  253 

W 

Waste  pipes,  cleaning  of,  357 
Water,  algae  in,  46 

characteristics  of,  34 

composition  of,  37 

forms  of,  34 

glass,  297 

hardness  in,  346 

in  foods,  35 

in  human  body,  35 

of  combination,  40 

of  crystallization,  41 

purification  of,  45 

supplies,  44 

synthesis  of,  39 

vapor  in  air,  79 

vapor  in  closed  space,  91 

value  of,  36 
Welsbach  mantel,  200 
Wesson  oil,  219 
White  arsenic,  285 
White  lead,  407 
White  metals,  384 
Wood's  metal,  289 


INDEX 


461 


Zeolyte  process,  349 
Zinc,   characteristics,   383 
occurrence,  382 
reduction  of,  382 


Zinc— Cont  'd 

uses,  384 
Zincates,  386 
Zinc  chloride,  385 

sulphate,  384 


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